The numbers show a clear trend: The more minority students a school has, and the lower the income level of their parents, the less time allotted for recess—nearly half of poor children go all day without it. They don’t even have anywhere to have it: In Chicago, nearly 100 elementary and middle schools have no playgrounds at all…

Repeated studies have shown that when recess is delayed, children pay less and less attention. They are more focused on days when they have recess. A major study in Pediatrics found that children with more than 15 minutes of recess a day were far better behaved in class than children who had shorter recess breaks or none at all.

They’ll get more out of class, too: Children seem to learn more efficiently when information is spaced out—when it is distributed over time. It’s been widely documented that the brain needs a break. High-performing East Asian schools have famously long school days—but much of the extra time is taken up by recess, not instruction.