Policies on inclusion are being increasingly embedded within education systems and teacher education across the world, with schools and teachers called upon to add 'inclusion' to their already large set of skills and tasks. There is, however, no consistent definition of what inclusion means or how it can be best promoted. The purpose of this paper is to explore the dilemmas that student teachers face when they encounter policy requirements to practice inclusion, and how they mediate the tensions. Drawing on two exploratory studies with science student teachers in two Initial Teacher Education programmes in England, we focus on the conceptions of inclusion held by the student teachers and the links between inclusion and teacher education. Our findings suggest that conventional understandings in relation to ability still dominate, with ability-based differentiation viewed as the key teaching strategy to promote inclusion. In addition, student teachers find themselves having to negotiate contradictory and often conflicting approaches to inclusion, diversity, and academic attainment. The discrepancies highlighted by this study have implications for how teacher education courses need to be organised to promote the practice of inclusion.