Most Helpful Guy
Well you should try to be around him, you shouldn't pay attention or flirt to other guys when he is in your vicinity or close to you and you should make every opportunities to go and talk to him and then you can tell him you like him.
Most Helpful Girl
When he's alone go up to his locker or something and be like hey I like you. and see what he says. If he doesn't like you which is highly doubtful, then that's the worse that can happen