Hard to say.

Apart from the legality of the situation, schools are taking on a huge responsibility when parents leave their kids there 6 hours a day. They obviously can't leash the kids but if you're going to mobilize a whole schools-worth of children you're responsible for you should have a plan to make sure none of them simply drift off and get killed in traffic. It being a middle school there are 12-13 year olds that shouldnt be as much of a problem but if I had a group of 11 year olds I was responsible for they'd be under a pretty close eye. Especially when moving everyone outside the building.

But who knows? There's probably something I'm not considering.