Period.8 by Chris Crutcher

Period .8 refers to Mr. Lodgson's class, where honesty is the best policy and everything is confidential, where you can talk about anything or nothing, and where you can skip without getting in trouble, but nobody ever does. Period .8 is the "safe place." Mr. Logs has respect for his students, and they have respect for each other. Everybody trusts that what they see is the truth.

Everything starts to go to hell when Paulie admits to his girlfriend Hannah that he cheated on her. He loves her and wants to explain himself, that it really isn't what she thinks, but she won't give him a chance at redemption. She's pissed, and he should definitely have known better. But as the story begins to unravel, more and more questions are raised without any clear answers. There's one guy, Arnie Stack, who seems to want to reassure everyone that everything is fine, and Paulie is convinced that Arnie knows more than he's letting on. And when Arnie sets his sights on the now single Hannah, Paulie sets out to prove it.

This is a mystery of a different sort, combining the traditional with the psychological, and mixing our emotions up all along the way. There's really intrigue here, and more than anyone's fair share of danger. It seems that nobody and nothing is off limits. 

Recommended to high school readers. There are lots more titles available from classic YA author Chris Crutcher.