The findings, published in the Archives of Pediatrics & Adolescent Medicine, come as U.S. schools in general cut physical activity time in favor of more academic test preparation.
Amika Singh, who worked on the study, said the findings meant that schools should prioritize both academics and exercise and that families could have the same attitude at home.
"Maybe it's an activity break, stand up every half an hour in class and do something," said Singh, from VU University Medical Center in Amsterdam.
"It might mean going to school by bike ... Any kind of physical activity you can think of. It doesn't mean only the physical education standard class."
Singh and her colleagues reviewed 14 studies that compared kids' physical activity with their grades or scores on math, language and general thinking and memory tests.
Those included two types of reports, such as 10 so-called "observational studies" in which researchers asked parents, teachers or students themselves how active they were, then followed them for a few months to a few years to track their academic performance.
In the four other studies, one group of kids was given extra time for physical education classes and other health and fitness exercises, and their test scores were later compared against a group of kids who didn't get extra exercise.
When researchers asked students how much time they spent exercising, they found that those with higher rates of physical activity did better in the classroom.
Three of the four studies involving an exercise intervention found that students given more exercise time scored higher on measures of academic performance.