Partner teacher stress

My worst student who I will refer to as 'Child Y' (which stands for, "Child, WHY do you keep doing this?") is giving one of my partner teacher's a lot of stress. Ever since we moved into the new building and his class changed into a smaller one he has become a real pain. Disrespectful, rude, arrogant, a bit of a bully and in general very poorly behaved. But only in my class, not my Korean partners.

I have discussed the matter several times with my partner and yesterday things seemingly reached a tipping point. In my class he upset another student. I dealt with the issue but the boy seemed to take no notice of me, however the upset child showed no signs of distress at all so I thought no more of it. I am told now that the boy went home and cried.

Of course my partner got a call from the mother today and she complained understandably. Then, my partner contacted the mother of 'Child Y' to tell the story and to basically complain about her boys behaviour, again. The mother of 'Child Y' then proceeded to moan, shout and complain about all this and ultimately seemed to blame me but in the process giving my partner a lot of stress. Thankfully my partner wasn't taking this lightly and argued our corner.

They talked for twenty minutes and seemingly got nowhere. The problem is that in the Korean teachers class he behaves but in the foreign teachers class - not just mine but the others that have taught him - he behaves terribly. We talked it over for a quite a long time but it was clear my partner teacher was really angry and stressed out. The simple fact is that now if he steps out of line in the he will be punished in the form of detention, called jaeshi at my academy. In fact if he continues I will just refuse to teach him, things are close to reaching that point. Students like this really stick in your throat because 95% of the rest behave fantastically. I wonder who he gets his behaviour from.