As schools everywhere strive to improve the academic performance of their students, many have cut physical education and recess periods to leave more time for sedentary classroom instruction.

A sensible new report from the Institute of Medicine, a unit of the National Academy of Sciences, shows how shortsighted this trend can be. It found that exercise can significantly improve children's cognitive abilities and their academic performance, as well as their health.

Students who exercise have lower body fat, greater muscular strength, and better cardiovascular and mental health.

While admitting that the studies are limited, a panel of experts assembled by the institute says that "a growing body of evidence" suggests children who are more active are better able to focus their attention, are quicker to perform simple tasks, and have better working memories and problem solving skills than less-active children.

They also perform better on standardized academic tests.

Academic performance is influenced by factors like parental involvement and socioeconomic status, but the panel reported that active children tended to have stronger performance, especially in reading and mathematics. It believes that the benefits of exercise during the school day outweigh the benefits from increasing class time.

The report recommends that all students get at least 60 minutes a day of vigorous or moderate physical activity, equivalent to a brisk walk. Only about half of all school-age children meet this guideline, according to the panel.

The way to increase exercise is to promote physical education classes, recess and classroom breaks during the school day; encouraging after-school sports and walking or biking to school when feasible would also help. Physical activity should be a core educational concern, not a dispensable option.