["European Journal of Education, Volume 61, Issue 3, September 2026. ", "\nABSTRACT\nIn this paper we draw on complex adaptive systems (CAS) theory to explore how changing systems of teacher education constrain attempts to introduce expanded sexuality education curricula. We report findings from a mixed methods study of teacher educators' perceptions of their provision in relation to England's statutory Relationships, Sex and Health Education (RSHE) curriculum. Despite its statutory status, RSHE remains unevenly and inconsistently embedded across initial teacher education programmes. We argue that sexuality education reform is unlikely to succeed without matched, sustained investment in teacher education—and that without this, statutory curricula risk generating new negative feedback loops rather than lasting change. We discuss implications for how policymakers might design more systemically coherent approaches to sexuality education reform.\n"]