Like many other Western countries, the Netherlands is faced with persistent ethnic and socioeconomic segregation, characterized by educational and economic inequalities, and indifference and sometimes hostility between different groups. Schools are in unique position to counter this segregation as they are responsible for providing equal educational opportunities and promoting positive intergroup relations. The success of this likely depends on the role of individual teachers. In this interlinked project, we will integrate Self-Determination Theory with the social identity perspective to study (a) how primary school teachers’ group attitudes and motivations to regulate prejudice shape their everyday teaching practices, and (b) how these practices ultimately contribute to students’ intergroup relations and group differences in educational adjustment. We will make a unique contribution by focusing on social class and ethnicity at the same time. Part-project 1 (PhD Jonne Bloem; department of Education) will focus on differential teaching practices toward students with different ethnic and socioeconomic backgrounds, and their consequences for students’ motivation, engagement and achievement. In part-project 2 (PhD Iris Boer; department of Interdisciplinary Social Sciences), we will examine teachers’ communications about ethnic and socioeconomic differences, and the impact thereof on students’ group attitudes and peer relations. We will use a three-wave longitudinal design (grade 5-6 primary school; 70 classes with 70 teachers and ±1800 children) and state-of-the-art methods, including experience sampling modelling, implicit measures, and sociometrics. Our results will be disseminated to educational practice, and provide important insights on how ethnic and socioeconomic diversity can be successfully dealt with in the classroom.