The book addresses a central problem of the German education system: the relationship between the social background of students and their academic success. This connection is particularly evident in the unequal distribution of students across the differentiated school types in secondary education, which largely occurs along lines of social origin. Even within a single school type, the development of students' competencies seems to be related to their social background. There are many plausible hypotheses about the causes of these primary educational disparities, but their empirical foundation is still weak. In particular, the contribution that the school itself makes to this issue has been little researched. The author explores this and other interesting questions within the framework of the SCHLAU panel study by examining the developments in competencies.