Early-childhood researchers and practitioners have become increasingly aware that schools must integrate social and emotional learning outcomes into curricula and instruction to maximize children's learning and well-being. Behavioral regulation, which falls under the broader self-management social and emotional learning competency, has been linked to various positive school and life outcomes. Because behavioral regulation is malleable in young children and critical for their successful academic performance, there has been a rise in behavioral regulation interventions across research and practice settings. Nevertheless, there is a shortage of ecologically valid, feasible methods for assessing young children's behavioral regulation in schools. The present study represents the first meta-analytic synthesis of the validity of a widely used early-childhood behavioral regulation measure, the Head-Toes-Knees-Shoulders task, in predicting children's academic achievement. A systematic review of the literature yielded 52 studies representing 354 effect sizes, 15,483 children, and 95 time points of data collection meeting the complete set of inclusion and exclusion criteria. Robust variance analysis demonstrated that the Head-Toes-Knees-Shoulders task was a valid indicator of children's academic achievement (r = 0.39) across literacy, oral language, and mathematics subject domains with little study-to-study variability. A moderator analysis indicated that consistent with prior research, the Head-Toes-Knees-Shoulders task was more strongly associated with children's mathematics performance relative to their performance on literacy and oral language measures. The results of this meta-analysis suggest that the Head-Toes-Knees-Shoulders task is an ecologically valid assessment with statistically significant, positive associations with children's overall academic performance. These associations remained stable across various conditions and circumstances and are consistent with or slightly stronger than meta-analyses examining the behavioral regulation and academic association with multiple measures of behavioral regulation. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]