For the last 3 months on and off, my 3 and a half year old son has been behaving aggressivly at nursery - hitting, pushing, pinching, scratching. He never used to do this at all - i used to see him being hit by other children in the park/playgroup etc and he would never retaliate. He seems to be making up for lost time now. A few months before this he started hitting and pinching his dad and me, and he's still doing it. This was after a stay in hospital, so i've always thought it could have been related to that. But the new development is hitting out at other children. It's not all the time, but he seems to 'turn' from being sweet and lovely to aggressive in a very unpredictable way. We always pick him up on it, and give him lots of praise when he's being good. But it's all getting a bit much and we feel at the end of our tether. I suppose what i'm wondering is if anyone has any thoughts on how you get a sense of what behaviour falls within the range of so-called 'normal' for a 3 year old and how do you know when it goes beyond that? I'm trying not to over-react but it's really depressing seeing him behave like this. (By the way, we have never hit him at all.)