school issue

So we've got a school issue. :( A few weeks back, I picked P up from school early and saw the assistant teacher pulling his arm to drag him out of the quiet corner. shocked I intervened and asked, "Is he not listening?" And she said, "He just kicked me...." His head teacher wasn't in the room to witness it. Mark and I talked about it and decided not to escalate the issue despite our uneasiness and would stay aware. Keep in mind he attends our local university's child development lab where there are almost always 5+ adults in his classroom of 20 children.

Fast fwd to this evening. I was just tucking P in bed and he told me he didn't want to go to school anymore. I asked if something happened at school today that he wanted to talk about and he said yes. I asked if it was something with his friends or teachers. To which he replied, "a teacher pulled my arm". Through further questioning (open-ended), he said it was the same teacher who has pulled his arm before. He said he was playing in the wood chips near the slide with four of his friends. I think a talk with his head teacher and/or the director is warranted at this point. I don't want to go in there with an accusatory tone and would like to know the best way to approach the situation. I really just want them to be aware of the issue and see if anyone may have witnessed the incident.

I feel like such a bad mother for not bringing up the first time. I just felt conflicted b/c he kicked her, not that it made her reaction right. She should have never laid her hands on my son. I don't want to make s at his school b/c they really take good care of him and don't want them to treat him unfairly for me complaining, KWIM? But then again, if it is a recurring problem it certainly needs to be addressed. P is calling her "the bad teacher".

I can't really talk with the teacher in question by myself. There is a huge language barrier.

What do you think? Thanks in advance.....