Anybody can sue anther person for anything at anytime. So think of another reason.
I don't need to. I strongly suspect that the reason the girl was suspended was 1) ignoring repeated requests to stop due to 2) fear of liability.
Don't think for one minute that had that child injured herself, the parents wouldn't be filing a lawsuit. If anyone can sue another person for anything at any time, as you say, the school did the right thing.
The kid got what she deserved. And the taxpayers will be breathe a sigh of relief.