According to social norms theory, when high school students overestimate the use of alcohol, tobacco, and other drugs (ATOD) by their peers, they tend to use more themselves. The purpose of this study was to determine whether these over estimations (misperceptions) could be corrected through a similar age peer-to-peer interactive social norms approach based on the Small Groups Social Norms-Challenging Model. The sample included 414 adolescents in health classes in five urban high schools. Baseline data were retrieved from the school district's Youth Risk Behavioral Survey (YRBS). Perception change was measured with items adapted from the YRBS. Results indicate a significant decrease in misperceptions from pretest to posttest. Student responses to open-ended questions indicate increased awareness of ATOD issues, positive plans for behavioral change, and positive program evaluation. Implications for use of the social norms approach is presented for high school teachers and administrators. (Contains 31 references, 2 tables, and 1 figure.)