This paper analyzes data from the "High School and Beyond" study on approximately 30,000 sophomores in 1,000 U.S. schools. The purpose is to explain the contradictory conclusions offered by two recent national studies on public and private schooling. The analysis examines differences between public and private school students in mathematics and reading achievement along racial and social class lines and for students in different programs of study. The results show that there are no public/private differences for wealthier whites, those who are the main clientele of the private schools, and for students in academic tracks. However, for minority and disadvantaged students and for students in the general track, there are small but statistically significant differences, some of which are due to differential selection. Policy decisions should not be based on the assumption that private schools produce better achievement outcomes than public schools. (Author)