A very similar thing happened to me way back when hitting was still acceptable in the yeshiva system. To make the story short, I was accused of something I did not do and the rebbe felt I needed “petch”. Well I got it good, several of them, both the palm of his hand as well as the back of his hand while I was trying to deflect the hitting, which of course made him more angry.
The point is that he was obviously not fit to be teaching nor had he received any sort of training. ALL our mechanchim should go through some sort of mandatory teacher training not just be someone that went to Kollel. By training I don’t mean just a seminar they may attend at the beginning of the school year, I mean real course work. There’s no reason a kollel can’t offer something like that, it is all for the cause of limud hatorah and can be conducted in classes with only men or women. It would also offer a chance for the Rosh Kollel to evaluate the mechanech prior to putting them in front of young impressionable minds.