This study examines the relationship between school norms of substance use disapproval (disapproval by the student body) and students' use of cigarettes, alcohol, and marijuana. Data came from nationally representative samples of 8th (N = 16,051), 10th (N = 13,251), and 12th (N = 8,797) grade students, attending 150, 140, and 142 schools, respectively. These students participated in the Monitoring the Future Project in 1999. Measures of school norms of disapproval of substance use were obtained by aggregating students' personal disapproval of daily cigarette use, heavy drinking, and marijuana use within each school. Analysis using logistic nonlinear hierarchical models indicated that in general, school-level disapproval lowered the probability of students' use of these substances, controlling for their own disapproval and for student and school demographic characteristics. The beneficial effect of school-level disapproval of cigarette and marijuana use on 8th-grade students' probability of daily cigarette use and marijuana use was significantly higher than it was for the 12th-grade students. The effect of school-level disapproval of heavy drinking on the probability of students' drinking was not significantly different across the three grades. Further, a school environment of disapproval was also found to create a protective environment for those students in the 8th and 10th grades who were themselves not disapproving of daily cigarette use. These results argue for prevention programs that include creation of an overarching environment of disapproval of substance use in schools.