Little ****s who think they run the place. For example, at school today when we were cramming before our Ancient History test, some kid from Year 9 or Year 10 or something is there playing his flute or some other crappy musical instrument, so one of us goes up to him and nicely asks that he stops. The kid just turns around and goes \"Dilay lo mo\" (not even sure on the spelling of it. It's something rude in Chinese). If it were anyone else who asked him and got that response, he would have had the snot beat out of him. He was just lucky it was a fairly nice guy.
That's only one example though. At our school (which is a selective school so you'd think it'd be better in terms of discipline etc. than most) the younger grades (hate to sound racist here, but they're 85% Asian) think they own the school, not paying any respect to older students or teachers. Hell, even the teachers were getting on our back at the end of last term telling us to intimidate them more!