Although research has established that school adjustment is associated with marijuana use (MU) in adolescence, few studies have tested these associations bidirectionally. Using random intercepts cross-lagged panel modeling, this study examined reciprocal associations between MU and school adjustment across 8th to 10th grade, including the transition to high school. Participants included 5470 rural adolescents (59% White, 41% Black) aged 12-17 years in 2002-2005. School adjustment factors predicted subsequent MU (i.e., higher self-reported grades were protective for Black and White youth; valuing education was protective for Black youth; school behavior problems predicted increased MU across the transition to high school for White youth). MU had several adverse effects on school adjustment, particularly during the transition to high school.