Childhood socioeconomic status (SES), as measured by parental education and family income, is highly predictive of academic achievement, but little is known about how specific cognitive systems shape SES disparities in achievement outcomes. This study investigated the extent to which executive function (EF) mediated associations between parental education and family income and changes in reading and math achievement in a sample of 336 children between the ages of 6 and 15 years from the NIH MRI Study of Normal Brain Development. Verbal memory was simultaneously modeled as a comparison candidate mediator. SES predicted significant changes in reading and math achievement over a two-year time period. Furthermore, executive function, but not verbal memory, was found to partially mediate the relationship between SES variables and change in math achievement. Collectively, these results suggest that executive function may be an important link between childhood SES and academic achievement.