This article analyses intergroup differences in education, with particular emphasis on schools offering one or more of the International Baccalaureate programmes ("IB World schools"). Experiences of human difference are often interpreted in terms of culture, and the notion of intercultural understanding is valued in many international schools. Yet intercultural encounters hardly differ from what social psychologists call "intergroup encounters". Social identity theory explains the dynamic of these encounters more effectively than models focusing on cultural difference. With reference to the contact hypothesis, this article presents suggestions as to how international schools can capitalize on their diversity by becoming practice grounds for intergroup encounters. (Contains 1 table.)