Trouble at Daycare

Troy changed from the young kids 1-3, to the older kids 3-6 at daycare last month. Troy really enjoys daycare and was looking forward to becoming a big kid. It seems like the transition has not been as smooth as I hoped for. He does not want to go to dc anymore, he tells me that one boy in particular, one of the oldest keeps being mean to him excluding him, and some have also called him names. He also tells me that he has no one to play with. I feel so bad for him, and I am not quite sure how this happened. He is so outgoing and happy all the time, that I was sure he would make friends right away, even though he is the youngest by far. I have talked to his teachers about this, and they keep telling me that he seems to be doing OK. OK is not good enough! I have decided that I am going to schedule an appointment with them to see what we can do about this. I am not going to sit back and accept that my boy is unhappy at dc, he spends way too much time there for him to not have a good time while he is there.