Research on the role of teachers in bringing about positive interethnic attitudes among their students has largely focused on the norms teachers express about cultural diversity in the classroom without considering teacher's enactment of these norms in their relationships with students. The current study assessed to what extent students' ethnic outgroup attitudes are affected by perceived positive teacher norms about cultural diversity, together with perceived positive teacher-classmate interactions that may serve as an example to students. We investigated whether and how teacher norms and practices interact to affect students' attitudes, and whether these effects may differ for minority and majority students. Data was gathered in two waves among 186 native (majority) Dutch students, and 129 students with a Turkish-Dutch, or Moroccan-Dutch (minority) background in 29 4th-6th grade classrooms. Results showed that both majority and minority students expressed more positive attitudes towards ethnic outgroups when they perceived their teacher to have a positive relationship with their majority classmates, but only when supported by positive teacher norms. Ethnic majority students had more favorable outgroup attitudes when perceiving positive teacher relationships with minority classmates, but only in the absence of positive teacher norms. These results indicate that students in culturally diverse classrooms consider their teachers' interpersonal relationships with classmates to inform their own attitudes about ethnic outgroups.