As preschoolers get older they get better and better at making their point with words so they no longer resort to physical aggression. As children travel the years from 1st to 3rd grade, most lose the impulse to attack others aggressively. An aggressive child may strike a sibling, but seldom would they hit a friend at school or on the play ground. You might see door slamming and feet stomping in the sanctity of home, but most third graders have enough controls to contain themselves at school. There are some children who continue to act out aggressively between 4th and 9th grade.
Boys display aggression in the form of direct confrontations and physical attacks.
Although girls seldom display physical aggression in this same age range, they act out aggressively by shunning, ostracizing and defaming others. Between the sexes, as children get older, there are few displays of overt conflict. Boys because of testosterone and because they have more muscle mass are more physically aggressive than girls. Children born aggressive have difficulty reading the subtle cues children send out in social situations. The aggressive child misreads the child's attempt to join his play, views it as hostile intrusion rather than one child simply wanting to play with another.