Since "public" education is mandated to be provided to everyone within a given age range regardless of mental ability, etc. incidents like these are bound to happen.

My brother - a psychology major - worked with ADHD and autistic kids for a while as a "guardian" - basically someone big and strong enough to physically restrain them when they got unruly. At 6'4"/260 (HS offensive lineman on state championship team), he is an imposing figure - and really handy to have around when you need to move that odd piano or gun safe. He would take them out to activities like parks and such to give their parents a few hours of sanity before taking them home. But he said that the job sometimes requires you to grab the kid and physically restrain them so they don't do something you can see is stupid and/or dangerous that their brains just don't process. He also said you'd be surprised how strong (and sometimes violent) these uninhibited kids can be.

The only solution to avoiding these kinds of scenarios is to put the onus of care back onto the parents instead of the teachers/school employees.