This article studied changes in rumor spreading and perceptions of peers' rumor spreading among students at one public junior high school following a social norms marketing campaign. Results of the study show that perceptions of peer rumor spreading fell following the campaign, but self-reports of rumor spreading did not decrease. Results suggest that a social norms marketing campaign conducted by a professional school counselor and delivered to students in a junior high can reduce misperceptions of negative social behaviors. (Contains 3 tables.)