Do you know of any information that would support or oppose my hypothesis that exercise will positively affect concentration in children?
This quote from the CDC study mentioned earlier provides an answer to your question: "Student physical activity may help improve academic performance including academic achievement (e.g., grades, standardized test scores); academic behavior (e.g., on-task behavior, attendance); and factors that can positively influence academic achievement (e.g. concentration, attention, improved classroom behavior). This report is a literature review that examines the existing research on the relationship between school-based physical activity, including physical education, and academic performance. It spans 23 years of research and includes 50 studies. The majority of the studies in this review report that physical activity was positively related to academic performance. Most importantly, adding time during the school day for physical activity does not appear to take away from academic performance. Schools should continue to offer and/or increase opportunities for student physical activity."