IN 1980, the late James S. Coleman, a prominent, University of Chicago sociologist, conducted a comprehensive study of student performance in secondary schools. This study was commissioned by the Department of Education, and many expected it simply to detail what types of school characteristics are associated with student success. Most observers were surprised then when Coleman focused on the importance of a single school characteristic: whether schools are public or private. Further, because Catholic schools constitute a large and relatively homogenous group in the private-school sector, Coleman and his two co-authors, Thomas Hoffer and Sally Kilgore, directed most of their attention to differences between Catholic and public schools.  They examined achievement test data and concluded that students in Catholic schools learn more than students in public schools. Moreover, Coleman rejected the claim that Catholic school students perform better on achievement tests simply because they are more talented or come from better families. He argued that the achievement differences between public and Catholic school students are, in significant measure, attributable to the different schools they attend.