Research Findings: Prior research has demonstrated the importance of young children's executive functioning (EF) skills for their success in schooling and beyond. However, the field lacks an understanding of how children's EF skills manifest in context. In the present study, we relate children's classroom off-task behavior to their EF skills. Prekindergarten children (N=263) were first assessed on their EF skills via direct assessments and a teacher report, and then they were observed on the amount of time spent off-task across classroom contexts like small-group instruction, whole-class instruction, independent work, transitions, and center time. Children's off-task behavior was weakly correlated with their directly assessed EF skills and moderately correlated with teacher reports of EF. The strength of associations was strongest for children's off-task behavior during whole-class instruction and transitions. Off-task behavior during whole-class instruction and transitions had the most within-classroom variation compared to other classroom settings, and off-task behavior during transitions most strongly predicted gains in math skills. Practice and Policy: Our study suggests that although direct EF assessments are the most predictive of children's academic achievement gains, it is beneficial to identify when children are going off-task and when this behavior is driven more by differences between children or classrooms.