Diverse samples of adolescents (n = 643) and young adults (n = 474) reported on how often they observed exclusionary behavior, how much they disapproved of such behavior, whether exclusion influenced their social and academic adjustment, and their academic grades and college plans. Perceptions of exclusion in school ecologies were distinguished from attitudes about exclusion and age-related differences were apparent. Among adolescents, norms apparent in school ecologies reflected concern with safety, achievement, social activism, and elitism. Attitudes reflected concerns with censorship, ambition, and the preservation of group boundaries. Among young adults, there were no common perceptions of school ecologies or attitudes toward exclusion. These findings offer definition to young people's awareness of whether exclusion promotes harm and feelings of disengagement in educational settings.