Did that kid come across as the kind that would become violent or threaten violence?
Even if he did, you don’t touch the kid unless he’s in midst attack of another kid.
From what I can see, yes. The principal could legally only react in kind. If the kid assaulted him he can defend himself. That shove was more than an "in kind" response.
But, there appears to be two special needs aides with the kid and I am mystified why they didn't do anything to control the kid. By law, they can restrain a kid who is potentially violent.
Before No Child Left Behind, this kid would have not been mainstreamed in a regular school. Our special ed department had their own dining hours and for extreme cases, they had their own kitchen facilities.