This article first presents some general information on the traditional tripartite system of education in Germany: Hauptschule, Realschule, Gymnasium. It describes the changes this system has undergone since the 1960s: because of the increased demand for schooling offering higher qualification certificates, the Hauptschule has declined in image and importance. The following passage shows both the political and social reasons that led to an experimental phase of the integrated comprehensive schools in all of the eleven states at the end of the 1960s. The integrated comprehensive school was not able to supersede the tripartite school system in the development of educational policies but only managed to be accepted as a fourth possibility. In the course of the experimental phase a wide, decentralized evaluation research programme was carried out. The most important results - horizontal mobility, equality of educational opportunity, school climate, academic achievement - are mentioned in context. The findings of the evaluation research programme do not provide any proof of the political failure of the educational reform in favour of a comprehensive system.