I'm not going to speculate on the exact cause but I'm comfortable saying children should have 2-3 recess periods outside totalling at least an hour (preferably

I'm not going to speculate on the exact cause but I'm comfortable saying children should have 2-3 recess periods outside totalling at least an hour (preferably 2 or 3) and that the recess periods should be structured to ensure that children spend time focusing on a variety of things at a variety of distances. There's certainly a possibility this won't have the intended effect but it will doubtlessly have a lot of net good effects assuming air quality cooperates.