I almost think I've imagined this book, because it's so bizarre and because I've had no luck in finding it.
I read it in about 1984. It's about a pretty blonde girl with nice clothes and hair who finds herself in a school where, mainly due to one bully, the "popular" crowd consists of overweight, ugly girls who have greasy hair and acne and wear ugly colours. The blonde girl, who is classically pretty, is tortured by the others about her looks.
