After reviewing research on national trends concerning private versus public schooling, the author examines how private school options in the Chicago metropolitan area might affect academic achievement for various demographic groups. Although the vast majority of students in suburban schools graduate from high school, with a high percentage going on to college, the four-year high school graduation rate in public schools in the City of Chicago is estimated at only 54 percent. Data from the Catholic Archdiocese of Chicago indicate that 97 percent of students in Catholic schools, which disproportionately serve low-income minority students, graduate from high school. Data from the "2000 Decennial Census of Population and Housing" suggest that private schools in the Chicago metropolitan area probably increase school enrollment rates for black and Hispanic students of high school age, thus increasing the probability that they will graduate from high school. Over the past 30 years, the number of Catholic schools in Chicago has declined by approximately 50 percent, and student enrollment in the remaining schools has also declined. The author concludes that fewer Chicago students are completing high school than would be the case if more students had access to private schools, especially students from black and Hispanic backgrounds. An additional outcome of this decline is that the cost of public education has increased more than would otherwise be the case as more students have been absorbed into public schools. (Contains 9 notes and 3 tables.)