School sector and educational context seem to make a difference in civic socialization. There is limited knowledge, however, of the mechanisms through which socialization may occur in public and private schools, and the extent to which they have any lasting effect. Does the private school effect on civic socialization persist into young adulthood, and if it does, what explains the effect? Analyzing data from NELS:88 using HLM, the results of this study show that, net of background controls, there is a private school effect on civic participation in young adulthood, but it is mediated through contextual factors in the family and school--such as parent-school involvement, intergenerational closure, student-teacher relationships and prior participation--that seem to account for the effect on adult civic behavior. (Contains 5 tables and 6 notes.)