Abstract
The objective of this article is to give a didactic presentation of the contribution of statistics to school effectiviness research. Our advice for the methodology of school effectiviness is not new. The contribution of this article is twofold: (a) precise formulation of the research question and (b) an evaluation of the existing methods as an answer to this question. We start from a precise definition of what we want to compute (estimate): the school effect. To make an unbiased estimate of the school effect, one has to take into account differences between the schools incoming students and differences between the schools in drop-outs. The starting-point for a possible solution for both of these problems in prediction on the basis of covariates. It is not guaranteed that this solution produces an unbiased estimate, but the solution will be better as more covariates are used as a basis for the prediction.
