This paper examines the causal effects of Catholic schooling on educational attainment. Using a novel instrumental-variable approach that exploits an exogenous shock to the Catholic school’s system, we show that the positive correlation between Catholic schooling and student outcomes is explained entirely by selection bias. The reforms occurring at the Second Vatican Council produced a dramatic exogenous change in the cost/benefit ratio of religious life in the Catholic Church. The decline of vocations that followed contributed to a significant increase in costs and in many cases to the closure of Catholic schools. We document that this decline was heterogeneous across US dioceses and more marked in those governed by a liberal bishop. We show that that the variation in the supply of female religious teachers across US dioceses is strongly related with Catholic schooling. Using the abrupt decline in female vocations as an instrument for Catholic schooling, we find no evidence of positive effects on student outcomes. Joint with Rania Gihleb.