This brief describes the findings of a study that tested preschoolers' executive function skills after participating in a program designed to enhance them vs. a standard curriculum. A total of 147 5-year-olds in their second year of preschool from a lower-income, urban school district participated in this study. The preschoolers were in 18 classrooms that were randomly assigned to either an executive function curriculum called "Tools of the Mind" or a standard academic curriculum that covered the same academic content but did not explicitly address executive function skills. Findings revealed that children who participated in the executive function curriculum performed better on the follow-up measures of executive function than children with the standard curriculum. Differences between children in these two groups were most pronounced on the more demanding tests of executive function skills. Second, for children in the executive function curriculum, performance on the follow-up measures correlated with independent measures of academic performance such as reading. In other words, children who improved in executive function skills also made improvements in other measures of academic performance. Children with the standard curriculum were tested only on executive function skills, not on academic performance, so no comparisons in these outcomes were possible.