So, this will be a wall of text, so be warned, but the story works best if you read it all the way through.
When I was fifteen or so, a girl, Georgia, started picking on a friend and I. It started out with taunting, teasing and insults, but when we failed to react, it escalated. She eventually resorted to punching us, kicking us, slapping us, slamming our heads down on desks every time she walked past us in lessons, jabbing us with sharpened pencils from behind, and once or twice she even got her posse to help out with a beating or two.