Marijuana remains one of the most frequently used drugs among adolescents and usage has increased in recent years. In addition to general use, many high school students use marijuana during the school day. The present study focused on achievement-linked correlates of in-school marijuana use by comparing non-users, general users, and school users on a set of school behaviors. The results showed that students who used marijuana in general exhibited poorer behavior on all measures than students who did not use marijuana; even stronger effects were found for school users. Students who used marijuana at school had lower grades, lower classroom participation, worse attendance, more academic dishonesty, and were disciplined more often compared to general marijuana users and nonusers. The relationships between marijuana use and achievement behaviors were similar for males and females, and for Black, White, and Hispanic students. Further research is needed on the motivational structures that underlie school-related drug use. (Contains 5 tables.)