This paper considers the role of private schools in an assessment of segregation in K-12 schools, with special reference to the south. It presents evidence to support two main conclusions. First, private schools have grown in importance in the south since 1960, in contrast to their declining importance in the rest of the country. This contrary trend can be attributed to the region's small proportion of Catholics, to its rising affluence, and to school desegregation. Because of the typically large areas covered by school districts in the south, private schools have offered white families an especially effective means of avoiding exposure to nonwhites in schools, particularly in counties with very high minority concentrations. In those counties, the rate at which whites enrolled in private schools tended to rise with the percentage of all students who were nonwhite, increasing sharply in counties over 60 percent nonwhite. Second, the paper measures the extent to which private schools contribute to segregation in schools in all regions. Using data on public and private enrollments in 1999-2000, the paper shows that private schools accounted for only about 17 percent of such segregation for the nation, with the bulk of segregation attributed to racial disparities between public and private school districts. For the nation, segregation increased between 1995-1996 and 1999-2000, and a rise in white private enrollments had a role in the increase. (Contains 12 references.) (Author/SM)