Who is right in this situation?

In art class, Kevin sits beside Peter, who is also his best friend. Peter is entertained by throwing pencils at the girl who is sitting in front of him. At the end of class, the teacher pulls Kevin and Peter aside and confronts them. Kevin wasn't throwing any pencils, but he still admits to doing it because he doesn't want to throw Peter under the bus. He feels that it would make him a d/ick if he told the teacher that he didn't do anything wrong. Kevin also believes that because Peter now owes him, he will follow through and do him a big favour. The teacher punishes them by making them write an apology letter and spending their next few art classes in the office. I think that Kevin should have stood up for himself and that it doesn't make him a d/ick for doing so- after all, Peter is getting punished anyways. I also don't think that Peter will repay him, as he's clearly not a decent person for a) throwing things at somebody for no reason and b) not sticking up for Kevin when he was falsely accused. What do you think Kevin should have done?