This article examines ethnic segregation in schools as a field where policy inaction, or non-decision making, is rife. A theoretical framework rooted in historical institutionalism and combining critical junctures with path dependencies enables the study of non-decision making and policy inaction. Moving from non-decision making as a general phenomenon to the specific case of British education policies, the focus is on ethnoreligious segregation between White British and South Asian Muslim students, which has become a salient issue in British politics and society. After a general discussion, the article zooms in on a North English town presenting typical constellations of ethnic segregation and mixing in neighbourhoods and schools. The subsequent policy analysis shows how, from the mid-1980s until recently, non-decision making has been predominant. Given the ongoing problematization of ethnic segregation in British politics and society, a reversal from policy inaction to formal decision-making seems possible. The article offers insight into the inner workings of non-decision making that have wider application, transcending any given locality and policy sphere.