The promotion of adult civic engagement is one of the primary goals of public schools. And the putatively negative effects of private schooling on civic engagement provide one of the most fundamental motivations for publicly provided schooling. In this study, I examine the comparative effects of Catholic and public high schools on adult voter participation and volunteering in the United States. I find that students who attended Catholic high schools are actually more likely to vote, though not volunteer, as adults. These estimated effects are robust to conditioning on a rich set of individual, family and community traits. I also present two-stage least squares estimates, which provide suggestive evidence that these results are not due to selection biases.