The aim of this paper is to provide an overview of the existing knowledge base about the impact of school leadership, mapping the different empirical and theoretical contributions to the field. Moreover, it examines and categorizes the research designs and models used in the different studies. The paper starts with a brief literature review of the impact of school leadership based on studies demonstrating the important role of school leadership and providing instructive insights of the impact of school leadership from the research paradigms of school effectiveness and school improvement, meta analyses and research projects explicitly focusing on school leadership. Mostly in the English speaking countries, but also in the Netherlands and to some degree in the Scandinavian Countries quantitative studies have shown that leadership is a central factor for the quality of a school (e.g. Reynolds, 1976; Mortimore et al., 1988; Sammons et al., 1995; Brookover et al., 1979; Teddlie & Stringfield, 1993; Leithwood et al, 2004; Marzano et al., 2005; Leithwood & Jantzi, 1999; Huber, 1999a, 2004; Muijs, 2007; Huber &Muijs, 2008). Qualitative studies on school development and improvement similarly emphasize the importance of school leaders, especially in view of the continuous improvement process targeted at an individual school (e.g. van Velzen et al., 1985; Stegö et al., 1987; Dalin & Rolff, 1990; Bolam et al., 1993; Fullan, 1993; Hopkins et al., 1996; Altrichter et al., 1998; Huber, 1999b, 2004). Meta-analyses have synthesized the evidence about the impact of school leadership, and have similarly pointed to the important role of leadership, as well as the impact of specific forms of leadership such as transformational leadership (e.g. Leithwood & Riehl, 2003; Robinson 2007; Marzano et al, 2005). Other studies have identified characteristics of successful leaders operating in different cultural circumstances (Day, 2005; Gurr et al., 2005; Höög & Johansson, 2005; Jacobson & Johnsen et al., 2005; Møller & Eggen et al., 2005; Wong, 2005). The studies mentioned above use a variety of research designs and strategies, but many cases are rather empirically oriented than theoretically grounded, only some studies attempting to build leadership theories, often using constructs taken from other fields like business studies, such as transformational leadership. The paper will provide an overview of current theories on leadership in education and a cathegorization of research strategies used in the different studies. Whilst mapping the field of leadership research, informed by previous work such as Gunter (2005), it is hoped to help the field develop further. Then it examines variables used to measure successful school leadership, concepts employed, and definitions used (Huber & Hiltmann, 2007), in order to develop a refined framework for leadership research. Moreover, the framework wants to integrate innovate ways to research leadership linked with organisational features taking the context and consistency into account

The paper is based on a rigorous review of the literature on the impact of school leadership as well as literature about research designs and methods. A range of databases will be consulted to search the literature, including ERIC, Educational Management Abstracts, British Education Abstracts and PSYCLIT. Content analysis methods will be employed to identify key themes to aid the construction of typologies and frameworks.

The aim of this paper is to work towards the development of models and typologies of research that take into account the context and complexity or educational organizations and environments and go beyond simple uni-directional causal models. Recommendations for methodologies will also be given.