Ok, I think the title was maybe about sixth or seventh grade, or possibly hairspray. Protag befriends an artsy loner weirdo who introduces her to the concept of third eyes and gets bullied by Xan (maybe Zan) the popular girl. At some point they have to paint sets, and Xan gets paint all over herself, either by accident or on purpose? Can’t quite remember.
Lost Classics of Teen Lit: Name That Book! 