This research project aims to get a profound insight into the magnitude, causes and consequences of social ethnic segregation in Flemish primary education. Although this social ethnic segregation is considered a social problem, in Flanders there is hardly any research dealing with it. First this project aims to describe the prevalence of social ethnic segregation in Flanders. Second, it will examine the determinants of this social ethnic segregation. And finally it will explore the effects of this social ethnic segregation for pupilsand teachers.