Education is one of the most important topics in the field of social inequality, and since the results of the PISA study, various scientific discussions have also resonated in the public sphere. The aim of this introduction is to provide an overview of the different lines of discussion in the sociology of education and their findings. This overview begins with historical educational research, which highlights the roots of some characteristics that still determine the education system today, such as its three-tier structure, but then also focuses on the issue of class-specific educational inequality. Both older and newer empirical studies on this topic and their respective theoretical foundations will be presented. The conclusion of this presentation addresses the question of ethnicity.