A systematic review of studies on leadership models in educational research from 1980 to 2014

Abstract

The purpose of this study is to reveal the extent to which different leadership models in education are studied, including the change in the trends of research on each model over time, the most prominent scholars working on each model, and the countries in which the articles are based. The analysis of the related literature was conducted by first employing a bibliometric analysis of the research and review papers indexed in the Web of Science database between 1980 and 2014. Then, a more in-depth analysis of selected papers was done using the content analysis method. The results showed that there has been increasing interest in leadership models in educational research over time. Distributed leadership, instructional leadership, teacher leadership, and transformational leadership are the most studied leadership models in educational research. It was also found that related research increasingly focuses on the effects of leaders on organizational behaviors/conditions and on student achievement. Accordingly, usage of quantitative methodology has significantly increased during the last decade. Possible reasons for these changes, implications, and recommendations for future research are also discussed.

Keywords

Bibliometrics distributed leadership instructional leadership leadership models leadership research teacher leadership transformational leadership

Introduction

The issue of leadership has been a matter of concern for hundreds of years and can be traced back to the philosophers of Ancient Greece, but the discussion of leadership and the need for effective leaders has hit the top in today’s world, where the achievement of individuals, organizations, and sectors depends substantially on the success of leaders (Bolden, 2004). Despite its importance, it is difficult to define leadership (Leithwood and Riehl, 2005). In fact, no single definition of leadership/leader exists in the literature (Bush, 2008; Yukl, 2002). Kruse (2013) has defined leadership as “a process of social influence, which maximizes the efforts of others, towards the achievement of a goal” (p.2). In accordance with this definition, Leithwood and Riehl (2003: 4) have stated that “at the core of most definitions of leadership are two functions: providing direction and exercising influence.” In an educational context, therefore, school leadership can refer to “the work of mobilizing and influencing others to articulate and achieve the school’s shared intentions and goals” (Leithwood and Riehl, 2005: 14).

In the educational sector, leadership began to garner attention during the beginning of the 20th century, when the scientific management theory was introduced with the aim of improving the quality and quantity of outcomes in the business sector. Following the scientific management theory, some other theories from the business sector, such as the functions of management theory by Fayol and the bureaucratic management theory by Weber, also influenced the way leadership was perceived in education (Lunenburg, 2003). However, there was also some level of awareness among scholars regarding the fact that the special characteristics of education and schools should be taken into account when considering leadership in the educational sector (Bush, 2003). This helped educational researchers to develop specific leadership models that are applicable to schools and other educational institutions, particularly within the last few decades. Therefore, many different leadership models, both from other sectors or specifically developed for the educational sector, have been discussed, implemented, and researched in educational settings for a long time.

Although leadership models have become a very popular subject in educational research, especially over the last three decades, the popularity of the specific leadership models over time and trends in the related literature are not very clear. Most of the systematic review studies on educational leadership included all types of educational leadership studies without paying special attention to the leadership models (see Hallinger, 2014, for more information on review studies in educational leadership). On the other hand, there have been only a few systematic review studies that were primarily interested in research on leadership models. These studies have generally focused on only one or, rarely, a few specific leadership models (e.g. Instructional, Distributed, Transformational) in detail (Bennett et al., 2003; Hallinger, 2003, 2005; Leithwood and Jantzi, 2005; Neumerski, 2013; Tian et al., 2016), rather than trying to explore the research trends in many different leadership models. Therefore, these review studies were able to analyze only a limited number of papers due to their scope and the nature of their work.

To this end, we believe that a more comprehensive review of existing research on leadership models in education can be made, drawing upon titles, keywords, and abstracts of papers published in prominent education journals. Therefore, the main purpose of this study is to conduct a comprehensive review of leadership models in education to reveal the extent to which different leadership models are studied, the changes in the trends of research on each model over time, the most prominent scholars and journals working on these models, and the countries in which articles are based through a bibliometric analysis of research and review papers indexed in the Web of Science database. In addition, we also analyzed the content of selected papers in order to obtain more in-depth information about the methods, purposes, and focus groups of the related studies. Analyzing a significant amount of literature in top journals would help researchers acquire a better picture of the change in the trends of research on leadership models. This would also provide an opportunity to interpret how leadership research has been influenced by the issues that educational systems have been faced with over time.

Leadership models in educational research

When it comes to education administration as an area of research, there was not much focus on school leadership before the 1900s. Back then, there was no explicit separation between school leadership roles and the teaching function (Murphy, 1995). During this time period, efforts to train people as leaders focused mostly on issues surrounding curriculum, instruction, and the description of eminent school leaders (Button, 1966; Callahan and Button, 1964). The understanding of leadership was largely shaped through ideas and pure reason rather than employing the data (Jacobson and Cypres, 2012). Therefore, no specific leadership model was observed in education during this period. After the 1900s, however, more concrete leadership theories and models started to emerge. Before going into the details of the most prominent leadership models used in education, we would like to briefly describe the development of earlier leadership theories, such as trait, behavioral, and situational, which provided a basis for discussions on leadership in different sectors.

Discussions about achieving more effective and efficient organizations have been overwhelming over the last century. While discussions about management types have mostly been concerned with what makes an organization more effective, leadership discussions have focused on understanding or identifying the leadership practices that can help to achieve an organization’s desired goals. In the late 19th and early 20th centuries, the “great man” theory was the popular phenomenon shaping the understanding of leadership. This theory assumed that leaders require specific qualities inherent in one’s personality, meaning that leaders are born with leadership qualities and acquiring such qualities afterward is not possible. The great man theory later evolved into the “trait theory,” which focused only on identifying leadership and non-leadership characteristics instead of making an argument regarding whether these characteristics are acquired or innate (Kirkpatrick and Locke, 1991).

Criticism of the trait theory led to the development of the “behavioral theory” of leadership. The behavioral theory was developed as a result of substantial research on understanding the type of leadership behaviors that resulted in effective organizations (Derue et al., 2011). The behavioral theory categorizes effective leadership behaviors into four groups, including task-oriented behavior, relational-oriented behavior, change-oriented behavior, and passive leadership. Task-oriented behaviors involve defining tasks, coordinating members, determining standards for task performance, and making sure that members meet these standards. Relational-oriented behaviors include a substantial focus on the quality of the relationships among group members. Change-oriented behaviors are concerned with driving change within the group through developing vision and motivating creative thinking and risk taking. For instance, many transformational leadership behaviors can be considered change-oriented. Finally, passive leaders refer to those who do not engage during times when no problem exists in the organization. Transactional leadership and laissez-faire leadership behaviors are more likely to represent passive leadership (Derue et al., 2011).

Leadership research from post-World War II through the 1980s was characterized by the behavioral science era (Murphy, 1995), and “the behavioral science approach was an attempt to reconcile the basic incongruency between the rational-economic model and the social model” (Lunenburg, 2003: 5). The specific leadership theory that emerged during this period was contingency/situational leadership. The situational leadership theory opposes trait and behavioral leadership theories that assert the existence of “best” characteristics and behaviors of leaders to influence subordinates. Followers of situational leadership theory center their ideas on the argument that there is no “best leadership practice” suitable to all contexts and situations; hence, effective leadership practices are highly dependent on the situation in which leaders work. Similarly, there is no “best method” for influencing subordinates due to their varying characteristics. “Rather, the task-relevant maturity levels of individuals or groups in a given situation tends to determine which leadership styles are likely to achieve the highest results” (Hersey et al., 1982: 217). For instance, followers who are not willing to perform specific tasks should be provided with clear directions and close supervision, while those who perform the tasks but have little confidence should be supported with two-way communication (Hersey et al., 1982).

While the discussions on leadership have a long history, most educational leadership models that have been discussed today, such as instructional leadership, distributed leadership, and teacher leadership, emerged during the post-behavioral-science era (after the 1980s). The post-behavioral-science era has been characterized by “the interrelated concepts of school improvement, democratic community, and social injustice, as well as subjectivist and interpretivist approaches to the study and practice of educational administration variously labeled neo-Marxist/critical theory and postmodernism” (Lunenburg, 2003: 5). As a result of the emphasis placed on the subjectivist and interpretivist perspectives, there has been a significant increase in the number of qualitative studies. The cornerstone of the development of school leadership models was research on effective schools. Effective school research was mostly qualitative and focused on schools that successfully created environments and conditions in which students could grow, irrespective of their socio-economic backgrounds (Clark et al., 1984). Findings of that body of research can be summarized thus: “School leaders matter, they are educationally significant, school leaders do make a difference” (Huber, 2004: 669). One of the main themes that emerged as a consequence of effective school research was the existence of strong leaders in the most successful schools (Austin, 1979; Bridges, 1982; Dougherty, 1981; Murnane, 1981; Purkey and Smith, 1983; Ralph and Fennessey, 1983). These studies played a key role in the development of new leadership models in education and the integration of leadership models from other organizations into schools.

After a brief background of the development of essential leadership theories, we now turn to the specific leadership models that have frequently been used in educational research. General information, such as the development and the content, about several prominent leadership models is provided in the following sections.

Managerial leadership

During the early 1900s, school leadership knowledge came under the heavy influence of Taylor’s scientific management theory, which was the dominating ideology of the time, exported from business research (Murphy, 1995). These years correspond to the “scientific management era,” during which school was seen more as a “rational-technical system” (Lunenburg, 2003) and hence the description of leadership practices failed to exceed the boundaries of the organizational and legal issues of schooling (Murphy, 1995). Following Taylor’s scientific management theory, Weber’s “ideal bureaucracy” and Fayol’s “universal list of management principles” contributed to the development of “classical management theory,” which shaped the understanding of characteristics of leadership in this era (Leonard and Leonard, 1999: 237). The influence of this era on today’s educational system is the indispensable existence of hierarchical and bureaucratic systems within schools (Candoli et al., 1997). Research on leadership during this time focused on the observable practices of leaders (Culbertson, 1988) and practices of effective school leaders were substantially related to the scientific management theory of organizations (Bush, 2003; Candoli et al., 1997). Such research constituted a base for the development of the “managerial leadership” model in education (Bush, 2007: 395).

Managerial leadership requires the leader to focus on “functions, tasks and behaviors.” When those are effectively carried out in an organization, people’s work can be facilitated. The behaviors of people are rational and authority is allocated among workers through formal positions within the bureaucratic hierarchy (Leithwood et al., 1999). The focus of this leadership model is on managing existing practices in schools rather than developing a vision beyond available practices. The model may be more visible in countries in which the educational system is centralized, since it considerably emphasizes the implementation of practices mandated by higher external management authorities within the bureaucratic hierarchy (Bush, 2007). Scientific management-based school leadership, however, fell short in addressing the social aspect of the school. A more humanitarian perspective, identified during the “human relations era,” dominated school administration research after the 1930s (Murphy, 1995) as a consequence of “the introduction of social sciences such as psychology, sociology, anthropology, and political science into the study of educational administration” (Jacobson and Cypres, 2012: 219). The major focus was on the relationship between school leaders and other staff and the human relations skills of leaders (Candoli et al., 1997).

Instructional leadership

A body of research during the 1960s and 1970s focused on the characteristics of effective school principals (e.g. Austin, 1979; Bridges, 1967; Chase and Guba, 1955; Edmonds, 1979; Goldman and Heald, 1968). The common theme that emerged from these studies was that an effective leader was a type of leader who paid considerable attention to the teaching and learning aspects of schools. Effective leaders were described as those who provided direction and strived to improve instructional practices (Chase and Guba, 1955); supervised teaching (Goldman and Heald, 1968); assessed the quality of instruction, gave feedback to staff, aligned instructional programs with school goals (Bridges, 1967); provided the motivational and material support required for the betterment of teaching; and established academic goals for students, worked on the development of instructional strategies, and monitored student progress (Edmonds, 1979). Such early efforts to provide an understanding of effective leadership established a basis for the emergence and development of instructional leadership theory, one of the most commonly studied types of leadership in the educational administration.

The idea of instructional leadership was ambiguous until the 1980s, when concrete models were introduced. The most cited instructional leadership model in the literature has been the one developed by Hallinger and Murphy (1985). This model defined instructional leadership through three components: Defining the school mission requires principals to frame and communicate schools’ goals; managing the instructional program suggests that principals coordinate the curriculum, supervise and assess the instruction, and monitor student progress; and finally promoting a positive school learning climate includes principals’ efforts to protect instructional time, provide incentives for teachers and learning, promote professional development, develop and enforce academic standards, and maintain high visibility. From this definition, it can be argued that the earlier understanding of instructional leadership was mostly principal-centered. However, a more democratic understanding of instructional leadership has started to appear in recent literature (Gumus and Akcaoglu, 2013; Lee et al., 2012; Marks and Printy, 2003; Neumerski, 2013). In addition, the usage of “learning-centered leadership” or “leadership for learning” terms has become widespread during the last decade. While providing a definition of instructional leadership, Bush (2003) used “learning-centered leadership” as a synonym for “instructional leadership” and “learning-centered leaders” interchangeably with “instructional leaders.” He further stated that “the term ‘instructional leadership’ derives from North America and it has been superseded in England and elsewhere by the notion of ‘learning-centered leadership’” (p.17).

Curriculum leadership

One of the key dimensions of instructional leadership is its focus on developing and coordinating an effective school curriculum. Besides the instructional leadership model, there exists a separate model representing the curriculum development responsibility of school leadership: curriculum leadership. The curriculum leadership model has been an important research topic in countries that have decentralized educational systems and, thereby, curriculum development is carried out at the school or district level (Law et al., 2007; Lo, 2012). A curriculum leader is someone who is responsible for monitoring, implementing, and improving curriculum (Lo, 2012). According to Pajak and McAfee (1992: 22) “school principals can provide curriculum leadership through decisions about staffing, supervision, scheduling, and the allocation of resources that facilitate the enactment of curriculum at the department level”.

Although it has a unique definition, the curriculum leadership model was sometimes used interchangeably with instructional leadership (Lee and Dimmock, 1999; Ylimaki, 2012). For instance, according to Lee and Dimmock (1999: 457) curriculum leadership involved multifaceted dimensions such as “goal setting and planning; monitoring, reviewing and developing the educational programme of the school; monitoring, reviewing and developing the staff of the school; culture building; and allocating resources.” The traditional view of curriculum leadership prioritized school principals as the unique personnel responsible for developing and improving schools’ curriculum. A new understanding of curriculum leadership has adopted a distributed leadership perspective and argues that teachers and other school personnel should be involved in the decision-making processes of curriculum design (Ho, 2010; Law et al., 2007; MacPherson et al., 1998).

Distributed leadership

Instructional leadership considers the principal to be a strong figure who is the unique person to coordinate and control multifaceted tasks relevant to curriculum and instruction (Goddard, 2003; Heck et al., 1990). Critics of this theory place their claim on the premise that school leaders cannot deal with such comprehensive tasks given that they are responsible for numerous time-consuming managerial tasks (Huber, 2004), and that leaders are more likely to possess less expertise than a subject matter teacher in a given subject area (Cuban, 1988). Therefore, a theory based on the distribution of leadership authority seemed inevitable. According to one distributed leadership perspective, “leadership practice is viewed as a product of the interactions of school leaders, followers, and their situation” (Spillane, 2005: 144). In such a context, “leadership is about learning together and constructing meaning and knowledge collectively and collaboratively” (Lambert, 1998: 5).

The nature of distributed leadership as a theory criticizes the hierarchical design of leadership and suggests the involvement of all personnel in the decision-making mechanism and collaboration among the entire staff as ways to effectively coordinate work and solutions to organizational problems. Distributed leadership has been well studied in educational settings during the last decade. Distributed leadership in the literature is often used interchangeably with other terms, such as “shared leadership,” “collaborative leadership,” “delegated leadership,” and “dispersed leadership” (Spillane, 2005).

Teacher leadership

The idea of distributing leadership functions, actions, and authorities to school personnel has led to a substantial body of research focusing on the question of how teachers might demonstrate leadership in schools. The development of the teacher leadership concept was primarily based on the research of North American scholars in the 1990s. Later, during the 2000s, it became a prominent topic in the UK as well (Harris, 2004). The teacher leadership concept “suggests that teachers rightly and importantly hold a central position in the ways schools operate and in the core functions of teaching and learning” (York-Barr and Duke, 2004: 255). It is based on the idea that all members of an organization can lead, and leadership is considered to be an agency that is distributed (Harris, 2004). Teacher leadership is carried out when teachers take part in the decision-making mechanism of schools, contribute to the professional development of others, share their expertise with their peers, and generate new ideas for the development of schools (Leithwood and Jantzi, 2000).

Transformational and charismatic leadership

Transformational leadership is another model that has been overwhelmingly used in educational research over the last three decades (Hallinger, 2003). Transformational leadership, which appeared in the leadership literature in the 1990s, was a reaction to the type of leadership that emphasizes hierarchy and top-down relationships (Leithwood and Poplin, 1992). It is often described in the literature as an opposite to transactional leadership (Avolio et al., 1999; Howell and Avolio, 1993), which suggests that principals are the primary responsible personnel for the coordination and flow of work (Huber, 2004). Bass (1998) identified four main components of transformational leadership: “idealized influence, inspirational motivation, intellectual stimulation, and individual consideration.” Such components provide a framework in which leadership is described as a product of multiple sources instead of one single authority (Hallinger, 2003).

“Transformational leaders motivate followers by raising their consciousness about the importance of organizational goals and by inspiring them to transcend their own self-interest for the sake of the organization” (Marks and Printy, 2003: 375). Given the emphasis of transformational leadership on the profound influence of leadership on followers, organizations, and societies, Shamir and Howell (1999) argued that transformational leadership highlights charisma and, therefore, should be a genre of charismatic leadership. Indeed, the conceptualization of transformational leadership by Bass (1998) was based on the extended version of charismatic leadership (Lowe et al., 1996). However, “apart from its central role in transformational leadership theory, charismatic leadership has been the basis of its own distinct literature” (Judge and Piccolo, 2004: 755). The characteristics of a charismatic leader include

communicating an ideological vision that is discrepant from the status quo, intellectually stimulating followers to think in new and different directions, communicating high expectations and confidence in followers, referring to followers’ worth and efficacy as individuals and as a collective, and engaging in exemplary and symbolic behavior and role modeling. (Howell and Shamir, 2005: 99)

Moral and ethical leadership

The inclination of transformational or charismatic leaders is not always positive. History has witnessed charismatic leaders whose actions and purposes are not acceptable or appropriate (Bush and Glover, 2014). Therefore, it was inevitable that ethical leadership fostering moral values would become an important component of educational leadership research. Trevino et al. (2000) identified two pillars of ethical leadership: moral person and moral manager. Their understanding was that

to be perceived as an ethical leader, it is not enough to just be an ethical person. An executive ethical leader must also find ways to focus the organization’s attention on ethics and values and to infuse the organization with principles that will guide the actions of all employees. (Trevino et al., 2000: 128).

A moral person has several traits, such as honesty, integrity, and trustworthiness; s/he has several behaviors, including doing the right thing, showing concern for people, and being open; and his/her decisions have several qualities, such as holding to values, objectiveness, concern for society, and following ethical decision rules. A moral manager is someone who becomes a role model through visible action, rewards people and maintains discipline, and communicates about ethics and values (Brown and Treviño, 2006; Trevino et al., 2000).

To sum up, the post-behavioral-science era has been characterized by the development of a number of significant leadership models in educational research, such as managerial leadership, instructional leadership, distributed leadership, transformational leadership, teacher leadership, and ethical leadership, as defined and summarized above. Besides these prominent models, several other models, including technology leadership (Anderson and Dexter, 2005; Davies, 2010), strategic leadership (Davies, 2003; Davies and Davies, 2006; Williams and Johnson, 2013), servant leadership (Cerit, 2009; Tate, 2003), visionary leadership (Aksu, 2009; Guskey, 2003), and authentic leadership (Begley, 2001, 2006; Branson, 2007) have also been used in educational research.

Method

In this study, the research on leadership models in the field of education was investigated through the bibliometric and content analysis methods. First, we used bibliometrics to draw the broader picture of educational research on leadership models by exploring the numbers and trends related to the journals, countries, leadership models, and authors. Then, we analyzed the content of selected papers in order to obtain more in-depth information about the methods, purposes, and focus groups of the related studies. Before providing the description of how the analysis was conducted, some information regarding the bibliometric analysis and rationale for selecting a specific database and time interval for the analysis will be explained.

Bibliometric analysis

“Bibliometrics is the application of mathematics and statistical methods to books and other media of communication” (Pritchard, 1969: 348). In other words, it is the use of statistical methods in the process of literature reviews to explore the trends of research on a subject (Young and Belanger, 1983). This method enables researchers to investigate the abstracts, keywords, and references of the studies in a particular field; to reveal and compare authors, countries, journals, and institutions in the field; and to bring out scientific collaboration and prominent researchers and journals. Although there has been an increase in the amount of bibliometrics in various academic fields, the method is relatively new to educational research. There is very little educational research using bibliometrics (e.g. Diem and Wolter, 2013; Phelan et al., 2000; Zawacki-Richter et al., 2010).

Rationale for the time and database restrictions

As identified earlier, our primary aim was to draw a general picture of how the related research has evolved over time by focusing on large numbers of existing studies rather than analyzing relatively low numbers of studies in detail. Given our scope, selecting a database on which we could search keywords, identify related papers, and obtain the information we needed for our analyses seemed to be necessary. Therefore, we decided to use the Web of Science database, since it indexes a large set of educational studies from highly respected journals all over the world. In addition, this database included detailed identifiers for each paper and was compatible with Vantage Point software, which is commonly used for conducting bibliometric analyses. We also only focused on studies published between 1980 and 2014. The reason for this specific time restriction was because the majority of educational leadership models that are still being studied were developed after 1980. In addition, the amount of research on leadership models in education before 1980 is very limited.

Data analysis procedures

We started our analysis with a total of 157,190 papers, including “articles” and “reviews” published in 334 journals in the field of “Education and Educational Research” indexed by the Web of Science database between 1980 and 2014. First, 1,191,735 Combined Keywords+Phrases were obtained by investigating the titles, abstracts, and keywords of those studies as revealed through the Vantage Point software. Then, the word “lead” was searched and 7455 keywords and phrases were listed. After listing all phrases and keywords that included the word “lead,” two researchers sorted out the ones thought to be related to leadership models. The list of keywords and phrases created by the two researchers was re-checked by the other two researchers involved in this study and the missing ones were added to the list. Working with the final list of the related phrases and keywords, two researchers separately developed lists of leadership models that are prevalent in the literature by categorizing keywords and phrases. One researcher developed a list that included 18 leadership models, while another developed one with 22 leadership models. The two lists were compared and discussed based on the existing literature. In the case of several controversial issues, researchers benefitted from the opinions of prominent researchers in the field. As a result, by combining some models (e.g. Ethical and Moral Leadership; Distributed, Shared, and Collaborative Leadership; Instructional and Learning-Centered Leadership) and removing models that had a focus outside of the K-12 level (e.g. Academic Leadership, Campus/University Leadership), researchers developed a consensus on keeping 14 leadership models in the study.

A total of 505 keywords and phrases were categorized under the final list of 14 leadership models. Then, a total of 709 articles that included at least one of these keywords and phrases were included in the study. Our preliminary analysis showed that two journals stood out in terms of publishing the most articles related to leadership models in education. Of the 709 articles, 107 of them were published in Educational Administration Quarterly (EAQ), which has been indexed in the Web of Science database since 1980. Educational Management, Administration and Leadership (EMAL) also published a significant number of articles (60) in its very short indexed period between 2009 and 2014, while the rest of the journals published 30 or fewer related articles. Based on these preliminary results, we decided to integrate the earlier volumes of EMAL, which were not indexed in the Web of Science database at the time of their publication, into our analyses to get a more complete picture. To do this, we visited the journal’s website and searched all the volumes published between 1980 and 2009. Two researchers carefully investigated all the papers published in these volumes to determine which were related to the above-mentioned 14 leadership models. What we did manually in this stage was very similar to what the Vantage Point software did automatically with a command for the papers indexed in the Web of Science database. This means that we simply read all the titles, abstracts, and keywords of hundreds of papers to search for keywords or phrases related to a leadership model. As a result, we found a total of 34 papers that included such keywords or phrases. We also identified the author(s), base country, and the related leadership model(s) for each paper in order to integrate them into our bibliometric analysis. Adding these 34 papers brought our total for the bibliometric analysis to 743. Thus, all the information presented in Tables 1 through 5 is based on these 743 papers.

Table 1.

The number of papers on leadership models in education research (1980–2014).

Years	f	%
1980–1984	16	2.2
1985–1989	23	3.1
1990–1994	47	6.3
1995–1999	44	5.9
2000–2004	77	10.4
2005–2009	192	25.8
2010–2014	344	46.3
Total	743	100

In the second part of our study, we used the content analysis method to obtain an in-depth understanding of the related research trends. Since the volume of papers we used for the bibliometric analysis was very large, we decided to choose two top journals, EAQ and EMAL, for the content analysis. These journals not only published the highest numbers of related papers, but also represented different parts of the world. While most of the EAQ papers in our bibliometric analysis were based in North America, EMAL published many papers from other parts of the world, such as Europe, Africa, East Asia, the Middle East, and Australia, in addition to a few papers from North America. In this stage, we aimed to answer three broad questions: (1) Which methods were used in selected studies? (2) What were the purposes of these studies? and (3) Which group(s) were focused on as leaders in these studies? Although we initially planned to answer these questions by investigating the abstracts of the papers, most of the time we had to go to the full papers and read them in detail to be able to obtain the information we needed. After investigating all of the selected papers, we found that more than 90% of the papers included in our bibliometric analysis from these two journals (183 of 201) were directly related to at least one leadership model. This confirmed the high relevancy of the papers used in the bibliometric analysis to the main focus of our study. Although the rest of the selected papers also included related keywords or phrases (that was why they were included in the bibliometric analysis), they did not focus on any leadership model as a main or sub-theme; rather, they only used related literature or made related suggestions based on their findings. Therefore, we have chosen to present only the content analysis of the 183 papers that directly related to leadership models in the second part of our findings section.

Findings

This section is divided into two sub-sections. The first section provides the results of the bibliometric analysis, drawing a broader picture of educational research on leadership models. The second section provides the results of the content analysis, including more in-depth information about the methods, purposes, and focus groups of selected papers.

The results of bibliometric analysis

We present the results of our bibliometric analysis in this section. First, we would like to introduce the general trends in research on leadership models over time. Table 1 shows the number of papers on leadership models in education research between 1980 and 2014.

When we examined the number of papers by year, we saw that interest in researching leadership models grew slowly until the 1990s. This interest seemed to remain stable until the year 2000. After 2000, the number of papers on leadership models started to increase again. Specifically, there was a dramatic increase after 2005. However, this figure should be analyzed with caution, as the number of education journals indexed in the Web of Science database also increased substantially after 2005. The number of education journals indexed in the Web of Science database was around 100 for more than two decades. The number passed 200 in 2010 with the new journals added to the database after 2005. The increase in the number of papers on leadership models could be a result of this change in the database. It was therefore important to look at each journal individually to better understand the trends of studies on leadership models in educational research. By doing this, we could also identify the specific journals that published the most papers about leadership models in education. Table 2 reveals the number of papers on leadership models published in education journals by five-year span.

Table 2.

Education journals that published the most papers on leadership models (1980–2014).

Journal name	Total	80–84	85–89	90–94	94–99	00–04	05–09	10–14
Educational Administration Quarterly	107	–	1	13	7	13	27	46
Educational Management Administration & Leadership	94	–	–	1	2	9	29	53
School Effectiveness and School Improvement	30	–	–	3	3	5	7	12
Elementary School Journal	24	–	1	4	7	2	2	8
Teaching and Teacher Education	23	–	–	1	1	1	8	12
Educational Leadership	21	9	2	2	–	2	6	–
Teachers College Record	16	–	1	–	1	5	6	3
Education as Change	15	–	–	–	–	–	1	14
Asia Pacific Education Review	13	–	–	–	–	–	4	9
Phi Delta Kappan	13	–	1	3	1	3	3	2
Urban Education	13	1	–	–	5	–	4	3
Education and Urban Society	11	–	2	1	–	3	3	2
Journal of Teacher Education	11	–	5	1	–	2	–	3
Asia-Pacific Education Researcher	10	–	–	–	–	–	3	7
Educational Sciences: Theory & Practice	10	–	–	–	–	–	–	10

Because more than a hundred journals in the Web of Science database published at least one paper on leadership models between 1980 and 2014, we only included a total of 16 education journals, which published at least 10 related papers (see Table 2). Among these journals, EAQ, which had been indexed in the Web of Science database since the beginning of this review (1980) has published the most papers (107) on the subject of leadership models. EMAL followed EAQ with 94 papers. Although EMAL was indexed in the Web of Science database beginning in 2009, we manually searched its earlier volumes back to 1980 and integrated related articles into our analyses as explained in the method section. Other education journals that published significant numbers of papers on leadership models were School Effectiveness and School Improvement (30), Elementary School Journal (24), Teaching and Teacher Education (23), and Educational Leadership (21).

In addition, Table 2 shows that a few journals added to the Web of Science database after 2005, such as Education as Change, Asia Pacific Education Review, Asia-Pacific Education Researcher, and Educational Sciences: Theory & Practice, have published important numbers of papers on leadership models. However, the numbers of papers published in these journals were not enough to fully explain the trends shown in Table 1. This means that there has been growing interest in research on leadership models after accounting for the increased number of journals indexed in the Web of Science database. When the most popular journals such as EAQ, EMAL, and School Effectiveness and School Improvement were examined in detail, the dramatic increase in the research on leadership models in education during the last decade was more clearly seen.

After introducing the number of articles published on leadership models by year and journal, we reveal the countries in which the articles were based. Table 3 shows the first 10 countries that were the sources for the articles on leadership models in education between 1980 and 2014. According to Table 3, a substantial number of the articles (296 of 743) on leadership models originated from the USA, as expected. The UK followed the USA with 67 articles, while the number of articles that originated from Australia and Canada were 46 and 32 respectively. South Africa and Turkey have also been important sources for the subject with 31 and 30 articles. When we looked at the source countries by year, we saw that the USA was almost the sole source of related studies until 1995. Then, several studies started to come from other countries, including Canada, Australia, the UK, and South Africa. After 2005, several countries, including Turkey, China, the Netherlands, Belgium, and Taiwan, became important sources for the studies on leadership models in education.

Table 3.

Number of papers by country.

Countries	Total	80–84	85–89	90–94	95–99	00–04	05–09	10–14
USA	296	4	7	18	19	46	86	116
UK	67	–	–	–	–	13	23	31
Australia	46	–	1	1	4	4	10	26
Canada	32	–	1	–	3	3	12	13
South Africa	31	–	–	–	1	2	5	23
Turkey	30	–	–	–	–	–	2	28
China	27	–	–	–	–	–	9	18
Netherlands	17	–	–	–	1	1	4	11
Belgium	15	–	–	–	–	1	5	9
Taiwan	13	–	–	–	–	–	4	9

So far we have focused on the research on leadership models in general. We have also conducted some analyses on the specific leadership models used in education research in order to show the most studied models, as well as the trends over time. Table 4 displays the number of articles related to each of the 14 leadership models specified earlier. According to the table, the most studied leadership models in education were as follows: Distributed/Collaborative Leadership, Instructional Leadership, Teacher Leadership, and Transformational leadership.

Table 4.

Number of papers on different leadership models.

Models	Total	80–84	85–89	90–94	95–99	00–04	05–09	10–14
Distributed/Collaborative Leadership	205	2	2	4	3	15	61	118
Instructional Leadership	181	11	9	18	8	15	35	85
Teacher Leadership	151	1	5	9	13	13	47	63
Transformational Leadership	147	-	4	13	7	16	32	75
Curriculum Leadership	49	-	2	2	1	8	16	20
Technology Leadership	46	-	-	2	1	5	13	25
Transactional Leadership	40	-	-	5	-	-	8	27
Ethical/Moral Leadership	38	1	-	1	5	8	8	15
Charismatic Leadership	27	-	1	4	-	5	6	11
Administrative/Managerial Leadership	21	1	1	2	7	2	3	5
Strategic Leadership	20	-	-	-	-	2	6	12
Authentic Leadership	18	-	-	-	1	-	8	9
Visionary Leadership	18	-	-	-	4	1	6	7
Servant Leadership	16	-	-	-	1	1	7	7

Note. Some papers focus on more than one leadership model, so they were included in two or more categories.

Analyzing Table 4 in detail shows that the Instructional Leadership model dominated the field from 1980 to 1995. Almost half of all of the studies on leadership models focused on instructional leadership until 1995. Then interest in Instructional Leadership decreased gradually until 2010, when the proportion of instructional leadership studies to all studies on leadership models started to increase again. Another interesting finding is about the trend in studies focused on the Distributed/Collaborative Leadership model. While there were only a few studies related to this leadership model until 2000, the number of studies increased gradually until 2005. According to the figures in Table 4, Distributed/Collaborative Leadership studies dominated the field after 2005. Teacher Leadership studies, on the other hand, have shown a more stable trend, with a rapid increase after 2005. Although teacher leadership became the second-most studied leadership model in education after the Distributed/Collaborative Leadership model between 2005 and 2009, it held the fourth position between 2010 and 2014. Studies on Transformational Leadership have been very stable after 1985. While interest peaked during the early 1990s, it continues to be one of the most popular leadership models in education. In addition, the number of studies on Charismatic Leadership has mostly gone up and down in line with the studies on Transformational Leadership. Lastly, Technology Leadership, Strategic Leadership, Servant Leadership, and Authentic Leadership models began to emerge mostly after 1995.

In the last part of our bibliometric analysis, we reveal the scholars who published the most articles on leadership models in education. Table 5 shows the top authors with the number of articles they published. In Table 5, we only display the publications about the most popular four leadership models. We identified 13 authors¹ who published at least six articles on leadership models. Philip Hallinger published 15 articles, most of which were about Instructional Leadership. Kenneth Leithwood followed Hallinger with 12 articles on different leadership models, but mainly focused on Transformational Leadership. Geert Devos published 11 articles on different leadership models, mostly on Distributed and Transformational leadership models. James Spillane published 10 articles that mostly focused on Distributed and Instructional Leadership. Both Ellen Goldring and Peter Sleegers published nine articles on leadership models in education. While Ellen Goldring mostly published on Instructional Leadership, most of Peter Sleegers’ works were about Transformational Leadership. Detailed information about authors’ publications by subject can be seen in Table 5. It should be noted that while most of the top publishing authors were from North America, several European scholars also published significant numbers of related articles, especially in the last decade.

Table 5.

The most published scholars by leadership model.

Author	Number of Papers	Distributed Leadership	Instructional Leadership	Teacher Leadership	Transformational Leadership
Hallinger, Philip	15	3	15	-	-
Leithwood, Kenneth	12	2	2	1	8
Devos, Geert	11	7	2	4	5
Spillane, James P	10	6	6	3	-
Goldring, Ellen B	9	-	8	-	1
Sleegers, Peter	9	1	2	-	6
Harris, Alma	7	7	-	4	-
Heck, Ronald H	7	4	7	-	-
Hulpia, Hester	7	7	-	4	1
Jantzi, Doris	6	1	-	1	3
Lee, Moosung	6	2	5	1	-
May, Henry	6	2	6	-	-
Murphy, Joseph	6	-	6	-	-

The results of content analysis

The content analysis of selected papers also revealed significant information about the research on leadership models in education. Our findings are based on 183 papers published in two prominent journals, EAQ and EMAL, between 1990 and 2014, as explained in the method section. Table 6 presents our categorization of these papers using three different lenses: method, purpose, and focused group. First, we grouped all of these papers into five categories in terms of their methodology, namely quantitative, qualitative, mixed method, theoretical and literature review, and systematic reviews. We differentiated systematic reviews from the theoretical and literature review category since those studies focused on certain numbers of papers from specific time periods and systematically analyzed them in order to answer their research question(s), while studies in the theoretical and literature review category used existing literature and theoretical discussions without a systematic analysis. Our results showed that the qualitative approach was the most used method in research on leadership models. However, the number of quantitative studies dramatically increased after 2010 and the quantitative approach became the most popular method in related research. The proportion of theoretical studies to all papers gradually decreased over time, while the number of papers that used mixed method and systematic reviews significantly increased after 2010.

Table 6.

Results of content analysis.

Theme	Total	90–94	95–99	00–04	05–09	10–14
Method
Quantitative	52	1	3	4	9	35
Qualitative	81	6	3	8	31	33
Mixed method	8	1	-	-	1	6
Theoretical and literature review	35	3	3	7	11	11
Systematic review	7	1	-	1	1	4
Purpose
Conceptualization	27	2	2	6	10	7
Perceptions and practices	77	5	2	4	27	39
Effects of leadership on organizational behaviors/conditions	42	2	3	7	9	21
Effects of leadership on student achievement	15	1	-	1	4	9
Leadership development	12	2	2	1	1	6
Other	10	-	-	1	2	7
Focused group
Principals	93	6	5	9	20	53
Teachers	34	4	1	2	10	17
Others (assistant principals, department heads, students, faculty members, etc.)	22	-	-	1	8	13
District leaders	9	-	-	1	5	3
No focused group	45	3	4	8	14	16

After identifying the trends in terms of methodology, we turned to the analysis of the purposes of the selected papers. We categorized the papers under five broad themes in terms of their purposes and created a sixth category (other) for those that did not fall into any theme. The first category included the conceptualization of certain leadership models or related theoretical discussions. The proportion of conceptualization papers to all papers gradually increased until 2005, when it started to decrease. The second category, perceptions and practices, was defined broadly and included papers that focused on the understanding or the implementation of the leadership models in practice. For example, studies focused on how leaders understand and perform their leadership roles related to certain leadership models, how contextual factors affect leadership practices, and how followers assess and think about the practices of their leaders. As seen in Table 6, this category included a significant number of existing related studies. The other two categories were effects of leadership on organizational behaviors/conditions and effects of leadership on student achievement. Studies in both categories have significantly increased during the last decade. While the former category included studies that focused on how leadership affects the behaviors, practices, motivation, etc. of different stakeholders (e.g. teachers, students, parents) as well as the organizational culture, effectiveness, capacity, etc., studies in the latter category specifically investigated the relationship between leadership and student achievement. The fifth category, leadership development, included relatively few studies that specifically focused on the preparation and development of leaders. Most of the studies in this category were theoretical or qualitative in nature and discussed models, practices, or specific programs within the framework of certain leadership models, such as instructional or distributed leadership. The last category, other, included a few papers we could not group into another category. Specifically, these papers focused on different topics with a specific emphasis on leadership models such as scale development, usage of certain scales, women’s leadership, etc.

Lastly, we investigated the focus groups of the selected papers. Focus groups were not necessarily the ones who participated in the studies, but the ones who were perceived as leaders. For example, teachers were surveyed or interviewed in many studies to obtain information about the leadership of their principles. In these studies, the principals were the focus group, since they were the ones whose leadership was focused on. In some studies, more than one group, such as principals, assistant principals, teachers, etc., were defined as leaders, so we identified more than one focus group for those studies.² However, there were also some studies that assessed or defined leadership in schools without referencing any specific group or that mentioned more than three groups as leaders. Similarly, most of the theoretical studies discussed leadership in general without focusing on any particular group. Therefore, we grouped those kinds of papers under the category of no focused group. When we looked at the trends in terms of the focus groups, we saw that most studies were primarily interested in the leadership of school principals. Even some papers that were about distributed or teacher leadership models focused on principals’ roles and how principals shared the leadership, etc. However, the number of studies that focused on the leadership of other groups, such as teachers and district leaders, have significantly increased in the last decade.

Discussion and conclusion

The purpose of this study was twofold. First, we aimed to reveal the changes in the trends of research on different leadership models over time, the journals that published the most related papers, the most prominent scholars working on these models, and the countries in which the related research was based by employing a bibliometric analysis of the research and review papers indexed in the Web of Science database between 1980 and 2014. Second, we explored detailed information about the methods, purposes, and focus groups of the existing studies on leadership models by using the content analysis method. For that part, we only analyzed related papers from two prominent journals, EAQ and EMAL, in order to obtain more in-depth knowledge.

First of all, our results clearly showed a growing interest in studying leadership models in educational settings over the last three decades. Furthermore, this interest substantially increased after the year 2000. This significant increase might be explained by several factors, such as the prominent trend of globalization, the internationally increasing accountability demands, the availability of more advanced statistical methods and big data sets, etc. For example, one effect of globalization on education is the increased competition among schools and nations with respect to student test scores. Many nations set clear goals to improve student learning outcomes, which in turn resulted in the accountability movement (Hursh, 2005). As a result, the need for effective leaders who can produce increased student learning outcomes has become even more substantial. At the same time, a significant amount of research has started to provide persuasive evidence with regard to the effects of leadership on educational outcomes with the availability of more advanced statistical methods and relevant data sets (e.g. Leithwood and Jantzi, 2000; Leithwood and Riehl, 2003, 2005; Leithwood et al., 2003, 2004, 2010). Therefore, these developments might have encouraged more researchers to focus on leadership models and their effects.

In terms of the specific leadership models, our analyses showed that distributed leadership is the most studied leadership model in educational research, although it is a relatively new model. Instructional leadership, which is one of the oldest educational leadership models, has also received significant attention from researchers. The third most studied model was found to be teacher leadership, followed closely by transformational leadership. When we looked at different time periods, we observed that studies related to the instructional leadership model dominated the field until 1995. Then, research interest in instructional leadership paused for around a decade, while the number of studies focused on other leadership models was growing gradually. However, the number of studies related to instructional leadership started to grow again after 2005, and increased even more during the last five years. It can be argued that research interest in instructional leadership in the last decade might have been influenced more by the current accountability demands and internationally increasing emphasis on student achievement, since it specifically focuses on leaders’ roles in instructional processes. From a similar perspective, the availability of more advanced statistical methods for measuring the specific effects of leadership on student achievement could also partly explain the dramatic increase in instructional leadership studies during the last five years. Whatever the reasons are, it is clear that the concept of instructional leadership has remained one of the most popular leadership models in the field of education over more than three decades. Similarly, Hallinger (2005) emphasized the persistence of interest in instructional leadership in his review of research on instructional leadership.

The results concerning specific leadership models also showed that the number of studies about distributed leadership has been enormous during the last decade, while there were only a few related studies in educational settings until 2000. This result is well aligned with the content of two previous review studies that specifically focused on distributed leadership research (Bennett et al., 2003; Tian et al., 2016). Our results also pointed out that the teacher leadership model has gained considerable attention during the last decade. Increased interest in these two leadership models illustrates an important change in understanding the leadership phenomenon. It seems that leadership is no longer attributed to a single person, which represents “the heroic leadership genre” (Spillane, 2005: 143); rather, it is viewed as a more “collective performance” (Gronn, 2002: 437). This trend might also have been influenced by the increasing accountability demands and decentralization movements in education, since these changes put significant pressures on local educational administrators. As a result, most people have come to the realization that achieving success for all students is hardly possible with the traditional understanding of leadership. A new definition of leadership based on the decentralization of power has gained prominence. The distributed perspective on leadership aims to advocate for involving all stakeholders in the schooling processes and holding them accountable for student learning outcomes (Leithwood, 2001).

Finally, besides well-grounded leadership models such as Instructional Leadership, Teacher Leadership, and Distributed Leadership, we found that some leadership models such as Strategic Leadership, Authentic Leadership, Visionary Leadership, and Servant Leadership have been emerging concepts in educational research during the last two decades. Citing Leithwood and Riehl (2003) and Bush and Glover (2003), Harris (2004) stated that despite the long-held discussions on leadership and a plethora of recent evidences of how leaders might influence student achievement, there is still not enough knowledge concerning what constitutes effective leadership practices. The development of new leadership models, therefore, can be explained as researchers’ endeavors to clarify the definition and practices of effective leadership from different perspectives. Given the current emphasis on the importance of leaders for organizations and schools in particular, we can anticipate more new leadership models to emerge in the coming years.

The results of this study also indicated that a high proportion of published papers on different leadership models were from the USA. It is already well known that most of the leadership research was initiated in the USA, so this result is not surprising. However, this could also be partly caused by the fact that many of the journals in the Web of Science database have origins in the USA. It was also found that related publications started to come from several other countries, such as the UK, Australia, and Canada, after 1995. After 2005, when many journals outside the USA were added to the database, related studies have come from countries around the world, such as South Africa, Turkey, and China. In accordance with these results, it was also found that North American scholars, such as Philip Hallinger, Kenneth Leithwood, and James Spillane, contributed the most studies to the research on leadership models in education. In addition, several European scholars, such as Geert Devos, Peter Sleegers, Alma Harris, and Hester Hulpia, have published significant numbers of related papers in recent years.

The second part of our review, the content analysis, also revealed some important information about the research trends in leadership models. First of all, it was found that the qualitative research method dominated the field until 2010. However, the proportion of quantitative studies to all related studies increased dramatically during the last five years. Increasing methodological diversity in leadership research has also been identified by earlier review studies (Hallinger and Chen, 2015; Heck and Hallinger, 2005; Tian et al., 2016). This might partly be caused by the salient development of statistical methods during the last decade. In addition, significant shifts in terms of the purposes of related research during the last five years might be another reason. The results showed that studies focusing on the effects of leadership on organizational behaviors/conditions or on student achievement have dramatically increased in the last five years. A recent book (Karadag, 2015) which includes meta-analysis review studies on the relationship between leadership and different organizational outcomes also shows a very similar trend. This trend might also impact the number of studies using quantitative methodology, since studies that have such purposes generally require statistical analyses. It is also noteworthy that increasing global accountability demands in the last decade might have boosted the number of studies focusing on the measurable effects of leadership models by using quantitative research methods.

Our content analysis also identified the groups that were perceived as leaders in selected papers. In line with the results of earlier review studies (Hallinger, 2011; Neumerski, 2013), our findings have also shown that school principals have been the most popular focus group in educational research on leadership models, followed by teachers. This trend has not changed very much over the years, while some other groups, such as assistant principals, department heads, district leaders, and university professors or administrators, began getting some attention during the last decade. In addition, studies that perceived leadership as a shared concept and defined or assessed it without focusing on any certain groups (or by focusing on more than three different groups) have increased during the last decade. Although these trends are well aligned with the findings of our bibliometric analysis in terms of the increased research interest in distributed forms of leadership during the last 10 years, it can be argued that most of the studies related to leadership models still perceive certain people as leaders and focus on their leadership practices.

This study makes an important contribution to the research on leadership models in education by reviewing a large number of studies indexed in the Web of Science database. The results of the study have provided significant insights about the development of related research and draw a big picture based on numerical evidence. However, the study also has some limitations, as all review studies do. First, while the authors spent significant time and effort to minimize mistakes such as missing information or incorrect categorization during the research process, from cleaning and categorizing the keywords for bibliometric analysis to the content analysis of the documents, there could still be some small mistakes given the nature of bibliometrics and the high volume of papers used in the analyses. In addition, our analyses do not include papers published in some of the well-known educational administration journals, such as the Journal of Educational Administration, International Journal of Educational Management, School Leadership and Management, and International Journal of Leadership in Education, since these journals were not indexed in the database we used in this study. Although not being able to include all the related journals or papers is a common problem of almost all review studies, excluding these important sources might be thought of as another limitation of our study. Therefore, we suggest that future review studies should focus on specific journals that were not included in this study. In addition, it might be argued that some over generalizations were made during the content analysis of documents, especially in terms of their purpose. Future research may narrow its scope based on our findings and select only one category, such as the effect of leadership on organizational behaviors or contextual factors affecting leadership practices, and carry out more in-depth analysis on the lower number of related studies.

Footnotes

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

Notes

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