The present study was designed to investigate the nature, timing, and correlates of motivational change among a large sample (N = 1051) of third- through eighth-grade students. Analyses of within-year changes in students' motivational orientations revealed that both intrinsic and extrinsic motivations decreased from fall to spring, with declines in intrinsic motivation especially pronounced for the adolescents and declines in extrinsic motivation especially pronounced for the elementary students. These changes in motivation were explained, in part, by shifts in students' perceptions of the school goal context. Findings suggested that typical age-related declines in intrinsic motivation may be minimized by a school-wide focus on mastery goals. Finally, the potential academic consequences of students' motivational orientations were examined with a series of hierarchical multiple regressions. Intrinsic motivation and classroom achievement appeared to influence one another in a positive and reciprocal fashion. Poor classroom performance minimally predicted higher levels of extrinsic motivation, but extrinsic motivation was not a source of low classroom grades. (Contains 2 figures and 3 tables.)