Concern for school-based homophobia is increasing, yet there is a tendency to focus on individual incidents of homophobic bullying rather than the cultural and institutional factors supporting them. We analyse ways in which institutional heteronormativity operates in primary schools and report results from our research in UK schools that culminated in a Participatory Action Research project in which practicing teachers explored possibilities for disrupting dominant discourses of sexuality and gender expression. We argue that policy and practice need to be reconceptualised to recognise institutional heteronormativity and to interrogate the discourses underpinning systematic forms of oppression.