Coleman formulated the thesis that social capital, which is rooted in social relations, provides certain options for action, such as, for example, the accumulation of human capital. Based on this theoretical assumption many authors in international research – mainly in the USA – investigated the effects of different forms of social capital on academic success. Therefore, the paper at hand focuses on the question whether the findings from abroad can be replicated for students in the secondary school system in Germany. Applying data of BiKS-8-14 and multi-level regressions, the effect of relations within and outside the family on school competences and grades is investigated. The results indicate on the one hand that for German students in secondary education their own social relations in school are important and on the other hand that effects vary in their meaning between the different school tracks.