You mean 12 years old? Yes they are immature, but oddly enough I did not encountered all that much uncontrollable pseudo masculinity in them. Someone occasionally acts in a way uncomfortable for girls, but it is usually considered "bad behavior" and he is called on that.
Maybe because such behavior is not considered "normal" here. They do display such behavior more often when they are in boys only group eg. physical education class. Not coincidentally, it is class where it is tolerated more.
