A meta analytical synthesis of school effectiveness research: The size of school effects and the effect size of educational leadership

In the field of school effectiveness research there is agrowing uncertainty about questions like which factors are responsible for differentiating between effective and non-effective schools, what is the real contribution of the significant factors, what are the true sizes of school effects and the extent of generalizability of school effectiveness results. One of the possibilities to address these questions is performing a meta-analysis. This paper deals with background of a meta-analytical approach as conducted by the University of Twente. Furthermore some preliminary results are presented. These results are related to the size of reported school effects and to the effect size of the variable educational leadership. With regard to first results will be presented for different sectors and subjects with an estimation of the boundaries where between the "true" effects maybe. Prior to the presentation of these results some persistent problems in the measurement of school effects will be dealt with. More specifically attentionwill be paid to problems like measurement error, specification in relevant levels and the choice of covariates. With regard to educational leadership, attention will be paid to the question whether educational leadership does have a significant relationship with student achievementand what the effect size of this variable might be