Although the rapidly expanding International Baccalaureate Diploma Programme (IBDP) is a well-recognized program perceived to offer best practices in education, including developing international mindedness in students and engaging with the local communities, there is little empirical evidence to support these outcomes. This mixed methods case study investigates if and how a diverse student body in one school (School X) contributes to the achievement of the International Baccalaureate Organization's aims, and in what ways student participation in the IBDP engages them with the diverse local community. This study concludes that engagement with the diverse local community was not perceived by participants as one of the main outcomes of offering the IBDP whereas the diversity of the school student body was perceived as an integral factor in helping students develop a wider worldview and international mindedness. Allport's social contact theory was used as a framework to explain the impact of diversity and help to understand it in the context of the IBDP.