- This paper reviews empirical evidence on the effect of the composition of a student body on academic achievement of students. After defining the term composition effect, methodological aspects regarding the study of composition effects are considered. International and national evidence for the composition of a student body with respect to students' abilities, social, and ethnic background is then presented. Whereas international studies find evidence for social, ethnic, and achievement composition variables, national studies reveal that mean achievement level of a school or class is the most important composition variable in Germany. However, this effect is confounded with school track and social composition, which itself exerts a small incremental effect. Ethnic composition, however, does not seem to play an important role. The paper closes with a presentation of the underlying processes of composition effects and a discussion on how the composition of a student body is considered in school governance practices.
