This report is one of a set of five that constitutes baseline descriptions and initial analyses of a very rich dataset. The report covers four major areas of interest in the comparison of public and private schools: student composition within the public and private sectors, resources available in these schools, the functioning of these schools, and the outcomes for students in the schools. The data and the analyses presented in this report are from the first (1980) wave of a longitudinal study. The responses are from questionnaires completed by representative samples of approximately 58,000 students in 1,015 public and private secondary schools, as well as their respective school officials. Catholic schools, which constitute about two-thirds of the total private sector, and other private schools are separately compared to public schools in the report. For some analyses, two additional sets of schools are included in the comparison. These are 11 high-performance private schools and a set of 12 high-performance public schools. Findings indicate that important factors in bringing about higher scholastic achievement in private and Catholic schools than in public schools are the greater academic demands and more ordered environment. The overall conclusion is made that the factual premises underlying policies that would facilitate use of private schools are much better supported on the whole than those underlying policies that would constrain their use. (Author/MLF)