No I meant effect as in hurt caused, that you really should not, etc.
Kids at 13 don't have the empathy that 18+ have.
Basicaly they are little self-centered monsters. Just old enough to manipulate effectively; too young to know you just can't do that sort of thing to someone.
Some people will teach them the hard way, usually fellow 13 year olds, by doing it right back at them.

I'm so glad I'm not a kid anymore!