The role of political socialization in explaining disengagement from specific modes of activism beyond voting remains largely unexplored, limited to date by available data and methods. While most previous studies have tended to propose explanations for disengagement linked to specific repertoires of political action, we propose a unified theory based on the different socialization experiences of subsequent generations. We test this theory using a new dataset of collated waves of the British Social Attitudes Survey and by applying age–period–cohort models for repeated cross-sectional data and generalized additive models to identify generational effects. We show that generational effects underlie the participatory decline across repertoires. Consistent with our expectations, the results reveal that the generation of “Thatcher’s Children” are much less likely to engage in a range of repertoires of political action than “Wilson/Callaghan’s Children”, who came of age in the more politicized 1960s and 1970s. Significantly, and in line with our theoretical expectations, the “Blair’s Babies” generation is the least politically engaged of all. We reflect on these findings and highlight the concerning implications of falling levels of activism for advanced democracies.