The so-called differentiated school system is a distinctive feature of education in Germany. While elementary school education is provided for all children in a single track system, students are allocated to different tracks in secondary schools (Hauptschule, Realschule, Gesamtschule, Gymnasium) according to their academic ability. Those tracks are typified on the basis of the number of grades, the study programmes and certificates they offer. In some of the federal states of Germany grade 5 and 6 represent a period of supervision and orientation with regard to the pupil’s future educational path. This ‘orientation stage’ is organised as a separate unit independent of the standard school types. In this case the secondary schools subsequently attended will begin with the 7th grade. Current attainment studies (PISA for example) found, that average student attainment and student composition differ greatly between the tracks of secondary schools (Opdenakker & Damme, 2001, 2006; Rumberger & Palardy, 2005; Weinert, Schrader & Helmke, 1989). In addition to this composition effect, there were institutional effects found at the end of the first phase of secondary education – after nine years of schooling and three years after leaving the orientation stage (see Baumert, Stanat & Watermann, 2006). Institutional effects in this context means that the students’ learning progress varies between the tracks, even when controlling for various intake characteristics. In other words, students with comparable background characteristics, comparable academic ability and of comparable intelligence perform differently depending on which school track they attend. According to this students do not only reach higher attainment levels if they attend the Gymnasium rather than a Hauptschule, but also – and this is even more striking – that they are given a greater education opportunity (and vice versa students at the Hauptschule are given lower opportunities). Thus, it could be demonstrated, that the differentiated school system in Germany promotes differential learning effects which are not intended and which stand in contradiction to the basic principle of the school system: equal learning opportunities for all children.

With data from a longitudinal achievement study in the federal state Hamburg (Germany) for students at the end of 6th grade, we can examine whether compositional and / or institutional effects occur already at an earlier stage in students’ school careers – three years earlier than it was shown with PISA data so far. As we use data from longitudinal research, we are able to control for prior knowledge and various background characteristics on individual level and for student composition on school level. We use Multilevel Analysis (HLM) to approach the influence of compositional and institutional effects.

At the end of 6th grade students in Hamburg leave the orientation stage and thus we do not expect to find institutional effects. This assumption is based on the consideration that the school system should guarantee educational mobility before students are allocated to different tracks at the beginning of grade 7.