In that instance it all comes down to potential liability. People will make mistakes and then try and avoid responsibility for their actions. Ultimately, the school is responsible should anything occur. Another missed opportunity. Instead of looking like an ass, a simple explanation why they can't play on school property would have been far more constructive.
Referencing liability in general.
Let's say I'm an old guy who happens to own a small field that includes a few trees adjacent to a subdivision. For decades kids have congregated to play baseball, tag, and whatnot. Let's say a kid trips and falls on a dead branch that had fallen from a tree. If there's an injury, let's say that stick struck the child in the eye, permanently blinding the child, I would bet dimes to dollars that in most cases the parents would be looking for damages and suing my ass. These days you need to cover your ass six way to Sunday, b/c people will not accept responsibility for their actions.
I recall when I was in school a kid got hit in the face with a snowball and it injured his eye. It's not an issue with snowball fights per se, it's the liability if a kid loses his/her eye. Same goes with dodgeball. I saw a kid get knocked clear off his feet from a ball to the face. Should that kid suffer a serious injury, aside from his bloody nose, it puts the school in a very difficult position.
