Having trouble with my 7 year old?

When my son is at school he acts like the perfect little angel. Teacher told me this morning how he is so respectful always uses his manors, greets everyone, and is a delight to have in cl. I kind of thought wow I'm surprised because he doesn't act like that at home. In fact his attitude at home is the opposite. This is new and just started. He just seems irritated with everyone. And he is upset by the silliest things. It started about a week before he went back to school from Christmas vacation. I thought maybe it was because he missed his friends, but he is still doing it. I asked him what is wrong and he says nothing is wrong. Last night was the worst, it was time to get a bath and get ready for bed, he asked to play wii and I said no because he had to be in bed in an hour. He took that as if I told him no wii for the rest of your life, he threw a fit, cried hysterically. At that point I made him go to bed because I figured he was tired. He was tired because Sunday night I had a lot of trouble getting him to bed, since he has almost 2 weeks off of school. His bed time is 8:30 every night and it has been that way since kindergarten, and we have never had any problems with him waking up the next day and getting through the day without being tired. But his attitude has to change. I can't have him start to walk all over me. Is the problem school, friends, us. I just don't know and like I said this is new, he is always happy and laughing but in the past week he's been acting as if he just wants left alone. Maybe he is coming to age and growing up, but I'm just confused. Any advise?