My son is nearly 4 and is a nice, polite, caring boy. His manners are spot on, he will help anyone no matter their age. His nursery have always said how kind he is but he seems like one of the few. The amount of boisterous, rude, arrogant kids from his nursery is ridiculous. The language 3 and 4 year olds are coming out with, the hitting, scratching I just hate it. I honestly fear for my son starting school. I'm not an over protective parent, I am parent that is raising my children to be good kind people. And it seems so many kids are just allowed to get away with whatever they like.
You can blame it on age all you like, but I don't think majority is "age" related.