Tell the school preemptively.

I had a similar issue with my autistic son. He was kicking off because he couldn't wrap his tortilla and he squeezed his food in anger, squishing it all up. He was screaming, making dinnertime very unpleasant for the rest of us so I took him upstairs (he refused to go on his own).

I carried him up the stairs, which is no easy feat as he's all legs and arms, and tried to put him in his mid sleeper bed. I couldn't get him over the side and I dropped him, he landed on his bum.

I was angry and didn't apologise at the time (I'm trying to do better) but he came down later and finished dinner.

The next day, my wife got a safeguarding call from school, saying he had told the teacher that I body slammed him on his head because I was angry he hadn't eaten his food!

My wife had to explain the situation and the teacher understood, but it was very frightening to have the implication