Ok so what should I do to flirt with him?

You don't say whether he already has a girlfriend, so I'll assume that he does not. If there is a big crowd of your age group there, you may struggle if you can't get him on his own somehow. Keep it simple. Be friendly but not too full on. When you both laugh at something together, reach out and touch his arm. Show an interest in his interests-if it's something that is not at all interesting to you, you're going to have to pretend that it is! Be supportive during the play - offer to help him read through his part, make an imaginary adjustment to his hair, etc. Compliment him on how well he is doing (even if he's terrible). Make a point of watching him, and make sure that he sees you watching him. If you're always around him, the message should get across! If you manage all of this, on the return journey in the car, make sure you sit next to him in the back. At some point put your hand on his and give him a smile. See what happens. Often the old fashioned approach is the best...Good luck