Within the literature on school leadership numerous concepts of leadership have been introduced during the last decades. Meta-analyses, synthesizing the evidence about the impact of school leadership point to the impact of specific forms of leadership such as transformational leadership (Leithwood & Riehl, 2003; Robinson 2007; Marzano et al, 2005). Other studies have focused on the shared responsibilities and leadership roles across schools giving rise to a distributed perspective of leadership (Spillane, Halversen and Diamond, 2001; Spillane, 2006). More recently, concepts such as integrated, total and system leadership have been introduced, which have attempted to extend leadership thinking to new concepts and areas (Fullan, 2004; Leithwood, Harris and Hopkins, 2008).

The paper consists of two parts. The first part maps different concepts of leadership; transactional leadership, transformational leadership, distributed leadership, system leadership, integrative leadership and total leadership by investigating the concepts’ origins, their aims and foci, expected outcomes and effects, processes and tools to achieve the outcomes, and actors and relationships involved. Most important, however, is what kind of theories of change (Dyson and Todd, 2006) underlie the different concepts.

A theory of change is "a systematic and cumulative theory of the links between activities, outcomes and contexts of the initiative" (Kubisch and Connell eds. 1998, p. 15-44). Theories of change identify goals/outcomes, assumptions underlying the approach, and change mechanisms through which change is supposed to occur. Understanding the theories of change will help us to develop clearer hypotheses of the extent to which a given approach is likely to lead to desired outcomes in school, and to develop useful strategies for school improvement through leadership.

Based on this investigation of the theoretical validity of the different concepts, the second part of the paper focuses on how the concepts are used in empirical research on leadership. By looking at different studies, the paper investigates the use of analytical perspectives to guide empirical research related to the research questions, the research design, the use of research methods and analytical techniques, not at least with respect to research findings and conclusions presented.

Connell, J. and A. Kubisch (1998) `Applying a Theory of Change Approach to the Evaluation of Comprehensive Community Initiatives: Progress, Prospects and Problems', in K. Fulbright-Anderson, A. Kubisch and J. Connell (eds) New Approaches to Evaluating Community Initiatives, vol. 2, Theory, Measurement, and Analysis. Washington, DC: Aspen Institute. Danziger, K. (1985). The methodological imperative in psychology. Philosophy of the Social Sciences, 15, 1-13. Dyson, A., & Todd, L. (2006). Theory of Change Evaluation and the Full Service Extended Schools Initiative. Paper Presented at EERA Annual Conference, Geneva, September 2006. Fullan, M. (2004). Leadership and Sustainability: System Thinkers in Action. London: Corwin Press. Leithwood, K., & Riehl, C. (2005). What we know about successful school leadership. In Firestone, W. & Riehl, C. (Eds.), A new agenda: Directions for research on educational leadership (pp. 22-47). New York: Teachers College Press. Marzano, R. J., McNulty, B. A., & Waters, T. (2005). School Leadership that Works: From Research to Results. Alexandra, VA: Association for Supervision and Curriculum Development. Robinson, V. (2007): The impact of leadership on student outcomes: Making sense of the evidence. Paper presented at the conference arranged by The Australian Council for Education Research . Slife, B. D. (1998). Raising the consciousness of researchers: Hidden assumptions in the behavioral sciences. Adapted Physical Activity Quarterly, 15, 208-221. Spillane, J. P. (2006). Distributed Leadership. San Francisco: Jossey- Bass. Spillane, J.P., Halverson, R., & Diamond, J.B. (2001). Investigating school leadership practice: A distributed perspective. Educational Researcher, 30 (3), 23–28 Yanchar, S. T., & Williams, D. D. (2006). Reconsidering the Compatibility Thesis and Eclecticism: Five Proposed Guidelines for Method Use. Educational Researcher,, 35(9), 3-12.