The aim of the paper is to provide an overview of variables used to measure successful school leadership, concepts employed, and definitions used (Huber & Hiltmann, 2007). Background In most international countries, the tasks and structures of schools and educational systems are changing. These changes have a particularly strong impact on the school leader's role. Consequently, questions of selecting, training and professionalizing of school leadership personnel have been emerging and been object of scientific research. This leads to the question about how successful school leadership - the success of school leaders - should be measured. While there has been research on the practical aspects of principal evaluation (e.g. Marcoulides, 1993; Hart, 1994), little is known about how the performance of school principals is operationalized in scientific studies. Research question The aim of the study is to investigate how the performance of school leaders is operationalized in scientific studies. What measurements are used to assess the performance of school principals in the field of research?

An extensive literature research was undertaken to find studies in which the performance of school leaders is being assessed. The literature research covered relevant electronic data bases form the fields of Psychology, Education, and Social Sciences (ERIC, FORIS, FIS, Psyndex, PsycInfo, SOLIS,) as well as a selection of scientific Journals from the mentioned fields. Each issue of the journals has been scanned for the period form 2008-1990. Additionally, each study found was scanned for cited studies that might be relevant. Studies were coded according to the following criteria: year, country, school type, number of performance measurements, kind of measurement (questionnaire, observation), focus of the measurement (e.g. outcome, behaviour, trait), source of evaluation (principal itself, teachers, parents, school administrators) etc.

Findings on the analysis of the coded studies will be presented with regard to the above mentioned coding criteria. The insight from the analysis of the measurements used in research to assess principals’ performance will be open for discussion on methodological aspects as well for practical implications.