Alcohol, tobacco, and other drugs are in the nation's schools, sidetracking kids from getting a good education and from building a solid foundation for a productive, healthy life. The good news is that a large-scale evaluation of Project ALERT, the widely used middle-school drug prevention program developed by the RAND Corporation, shows that it successfully alters the course of substance use for many youth. The program even helps high-risk youth, who critics claim are beyond reach. This Research Highlight summarizes results from the Project ALERT evaluation, along with outcomes from related studies showing that adolescents who continue to drink and smoke face increased academic, social, and behavioral problems later in life. (Contains 4 figures.) [This Highlight summarizes RAND Health research reported in the following publications: (1) Ellickson, Phyllis L., Daniel F. McCaffrey, Bonnie Ghosh-Dastidar, and Douglas L. Longshore, "New Inroads in Preventing Adolescent Drug Use: Results from a Large-Scale Trial of Project ALERT in Middle Schools," American Journal of Public Health, 93(11), 1830-1836, 2003; (2) Ellickson, Phyllis L., Joan S. Tucker, and David J. Klein, "Ten-Year Prospective Study of Public Health Problems Associated with Early Drinking," Pediatrics, 111(5), 949-955, 2003; and (3) Tucker, Joan S., Phyllis L. Ellickson, and David J. Klein, "Five-Year Prospective Study of Risk Factors for Daily Smoking in Adolescence Among Early Nonsmokers and Experimenters," Journal of Applied Social Psychology, 32(8), 1588-1603, 2002; also RAND Corporation, RP-1060, 2003.]