My youngest ds turns five on February. He started school in August, one of the youngest in his class. His teacher pulled me aside today to tell me that he has been hitting other children today and dug his nails into another child's hand. 
At home he is usually very well behaved. He and his older brother do occasionally hit each other but it's dealt with consistently and as soon as possible.
I have for children altogether and have never had to deal with hitting. It just hasn't occurred. My youngest has been through a lot though. His dad and I split when he was 14 months. I've had to move three times though thankfully settled now. He was in a nursery but this is a new school.
He does lack some self confidence and can be clingy at times.
I'd like to support the school and put a stop to his behaviour. I do feel they are making him out to be very bad, but I'm probably a bit overprotective. He has been through a hitting phase when he first started but it petered off which the teacher acknowledged.
Now whilst I want to reinforce he can't be hurting other children, at his age I do believe it needs to be properly dealt with when it actually happens. Me picking him up at the end of the school day and telling him off for something that happened in the morning seems a bit pointless. I'm not saying however it should just be up to the school. Could anyone advise on what I could do here? Tia.