Because most youth are enrolled in school for many years before they initiate sex and when they initiate sex, schools have the potential for reducing adolescent sexual risk-taking. This paper reviews studies which examine the impact upon sexual risk-taking of school involvement, school characteristics, specific programs in school that do not address sexual behavior, and specific programs that do address sexual risk-taking. Multiple studies support several conclusions. First, involvement in and attachment to school and plans to attend higher education are all related to less sexual risk-taking and lower pregnancy rates. Second, students in schools with manifestations of poverty and disorganization are more likely to become pregnant. Third, some school programs specifically designed to increase attachment to school or reduce school dropout effectively delayed sex or reduced pregnancy rate, even when they did not address sexuality. Fourth, sex and HIV education programs do not increase sexual behavior, and some programs decrease sexual activity and increase condom or contraceptive use. Fifth, school-based clinics and school condom-availability programs do not increase sexual activity, and either may or may not increase condom or contraceptive use. Other studies reveal that there is very broad support for comprehensive sex- and HIV-education programs, and accordingly, most youth receive some amount of sex or HIV education. However, important topics are not covered in many schools.