1.5 hours of recess daily minimum or bust for 3rd grade and under, I say, and I think that's not quite enough, really. Screw this 30 minutes crap. Know how I can guarantee my kids have behavior problems at home? Coop them up inside all day. Know how I make a day run smoothly? Make sure they're outside running around at least a couple hours while the sun's up. Then consider that they're giving a bunch of them nearsightedness on top of definitely creating behavioral and learning problems. It's crazy.