A study conducted at Mount San Antonio College (MSAC), California, to determine trends in the number of high school graduates in the MSAC district; the percentage of high school graduates attending MSAC; retention in district high schools between the ninth and twelfth grade; high school performance on California Assessment Program (CAP) Tests; differences among students from district and non-district high schools; K-12 enrollments in public and private schools in the district; and K-12 ethnic distributions in MSAC district schools. Study findings included the following: (1) while private schools have experienced continued enrollment growth since 1971, public high school enrollments have fluctuated; (2) the percentage of district high school graduates attending MSAC dropped from 22.2% of the private high school graduates and 23.4% of the public high school graduates in 1984-85 to 20.4% of the private school graduates and 21.7% of the public school graduates in 1987-88; (3) there was an overall district loss of 2,715 students, or 22.15%, between the ninth grade in 1985 and the twelfth grade in 1988; (4) 10 district high schools and 2 continuation schools scored above the state average on the CAP reading tests and 12 high schools and 8 continuation schools were below the state average; and (5) K-12 enrollments were 1.58% higher in 1988 than in 1987. (AYC)