There is a broad consensus in research, politics and society in general that educational success of young people should not be correlated with their background characteristics such as gender, migration background or socioeconomic status (SES) of their families. However in all European countries, empirical studies reveal a strong connection between the SES of families and the educational success of their children. This finding motivates the extensive research that deals with social disparities in education at the intersection between social science and educational science. With this paper we present an overview on this field of research and thereby give an introduction to the topic of this symposium “Social Disparities in Educational Research”. We will outline the theoretical foundations and discuss different methods to measure SES with questionnaires. On this basis, we then present empirical findings from international large-scale studies of student achievement like PISA, PIRLS, and TIMSS, name background characteristics which might moderate the connection between SES and school achievement, and, finally, reveal central desiderata for future research. Furthermore we will introduce the topics of the other eight symposium papers.