My son has always been a very placid easy going, lovely natured boy. Since he went back to school in year two, he is regularly losing his temper, being aggressive and rude to me. He has never done this before, but he is acting like he is psychotically tired. This seems to happen at least a couple of times a week. He has a younger sister of four whom he gets along with really well most of the time. He is also starting to not want to kiss us goodbye at school. Is this a growing up stage? He is worrying me as there has been no sort of domestic upheaval.