June becomes Billy's tutor after his father finds out he failed his first english test. As much as Billy loathes talking about english for an hour and a half, there's something about June that keeps him coming back.
It's not Lance's fault he's failing music, it's the fact that he got stuck with the trombone. So when his mom insists on getting him a tutor, he was expecting some loser who actually enjoys the trombone.
He was /not/ expecting Keith freaking Kogane to give him a fucking tromboner.