Despite the recent resurgence of academic interest in nonpublic schools, we continue to be relatively ignorant of the political and social composition of these schools. This study of the Chicago and Los Angeles Catholic school systems sought to redress this ignorance. The study first gathered and analyzed school data from central (diocesan) sources, then described and analyzed the internal policymaking structure of each local school, and lastly surveyed and analyzed parental motivation, with the following question as the basis of the survey: Why do parents initially send and ultimately maintain their children in nonpublic schools? The report concludes that the systems vary in their character, but are locally controlled; and that parents support schools despite differences with religious, racial, or pedagogical policy--with or without formal participation in policymaking institutions. The research points to the important role of local school vulnerability in drawing support and to the role of parental confidence in teachers, which may be aided by the character of the local school's educational bureaucracy. (Author)