Age differences in intrinsic and extrinsic motivation and the relationships of each to academic outcomes were examined in an ethnically diverse sample of 797 3rd-grade through 8th-grade children. Using independent measures, the authors found intrinsic and extrinsic motivation to be only moderately correlated, suggesting that they may be largely orthogonal dimensions of motivation in school. Consistent with previous research, intrinsic motivation showed a significant linear decrease from 3rd grade through 8th grade and proved positively correlated with children's grades and standardized test scores at all grade levels. Extrinsic motivation showed few differences across grade levels and proved negatively correlated with academic outcomes. Surprisingly few differences based on children's sex or ethnicity were found. Causes and consequences of the disturbingly low levels of motivation for older, relative to younger, children are discussed.