AbstractIn this paper we draw attention to an innovation, mixed sex grouping, which is increasingly featuring in the secondary school PE curriculum. The discussion considers the motivations which underpin this organisational change and examines what it means for the professional identities of teachers and their classroom practices. The paper also focuses on the process of differentiation in PE classrooms and suggests that in some circumstances innovations of this sort can exacerbate rather than attenuate childrens and teachers stereotypical attitudes.