The Confession by R L Stine
Fear Street - Where your worst nightmare lives... Julie's friends couldn't stand Al. In fact, they all wished Al were dead. But that doesn't mean one of them killed him. Julie knows her friends. She knows they're innocent... until one of them confesses to the murder. Julie and her friends make a pact to keep the killer's secret. They're sure it was just a one-off thing. It will never happen again. ...Will it?