Converging findings in psychology, neuroscience, education, and economics suggests that child persistence in learning represents an important determinant of academic success during the school years. Nevertheless, the developmental origins of productive learning behaviors are not well understood. Some findings suggest that executive function skills may be developmental precursors to learning-related behaviors. The present study examines how toddler working memory skills predict subsequent achievement and classroom engagement in kindergarten. Participants are 1824 children from the Quebec Longitudinal Study of Child Development. Children were individually assessed on working memory at age 29 and 41 months, using the Imitation Sorting Task. When children were 74 months of age, kindergarten teachers rated classroom engagement and trained examiners assessed number knowledge and receptive vocabulary. Multiple regression analyses revealed a positive prospective association between early working memory scores and later classroom engagement, ("standardized [beta]" = 0.076), number knowledge, ("standardized [beta]" = 0.133), and receptive vocabulary ("standardized [beta]" = 0.059). These results were above and beyond child sex, verbal and nonverbal intellectual skills, and socioeconomic status. The findings propose a robust, easily accessible, and cost effective assessment method of early childhood executive function for the development of early childhood interventions that improve school readiness. (Contains 3 tables.)