The study described in this report investigated the perceptions held by public school administrators concerning the effects of private schools on the operation of public schools. Questionnaires were completed and returned by several randomly selected principals and the superintendent of public schools in each of 41 American cities with populations between 100,000 and 200,000. Respondents indicated the strength with which they perceived 23 postulated effects to operate in their cities with reference, first, to systemic private schools (members of national, religiously supported systems) and, secondly, to independent private schools (not identified with any formal system). In general, respondents perceived the effects of private schools on public schools to be negligible in impact. Responses were analyzed statistically to determine the nature of perceived private school effects on public schools (both in general and in terms of the systemic-independent distinction), and to examine some characteristics of variance among these perceptions. Interviews were then conducted with a sample of participants in seven cities. The major result of the interviews was the finding that participants in general lacked concern for, interest in, and familiarity with private schools or their effects on public schools. (Author/MLF)