Bullying, cyberbullying, and sexual harassment in high school occur in the presence of peers, who often implicitly or explicitly support this perpetration. This study examines the impact of a social norms campaign on personal and perceived peer norms related to bullying, cyberbullying, and sexual harassment. Wilcoxon signed ranks tests indicate that personal norms became more prosocial (i.e., less acceptance of and engagement in perpetration) following the intervention, and that personal and perceived peer norms were significantly different from one another, with personal norms being more prosocial, both before and after intervention delivery. However, change was not significant for perceived peer norms from pre-test to post-test. Future work would benefit from examining the utility of the social norms approach on bullying and sexual harassment in high school on a larger scale. [This is the in press version of an article published in "Journal of School Violence."]