When I was called in to discuss my son's behavour under similar circumstances last term I was taken completely by surprise as his behaviour at home, and at other peoples' houses, had always been really good.
I was so shocked I just kept apologising and saying I'd have a really serious talk with him to see if we could get to the bottom of it.
(Aparently he had told a girl he was going to kill her and pulled up the skirt of another girl in the playground).
I talked to him, but couldn't really make any more sense of the alleged incident.
Later however he did talk about being teased by girls and didn't want to go to school because the girls were 'horrible' to him.
When the teacher first called me in I assumed my ds must be terrible and displaying notable signs of disfunction - otherwise why on earth would she call me in? I was very upset and couldn't understand it at all.
I was relieved when the summer holidays came. There was still, and remains to this day, absolutely no sign of the behaviour his former teacher described.
I retrospect I'm angry to have been put through this unecessarily. I really felt like a failing parent with a weird problem kid. All for nothing.
I'm all for teachers keeping parents in touch with any difficulties which arise, as there may well be a link to a problem at home. But IME the problem was at school and I felt unjustly blamed.