Answer:
Wear a short skirt to school and don't let him see your knickers, but every time he's around make him think he's going to. Play with your skirt, sit with it pulled half way up your legs, lift it when you hitch up your tights, twirl around so it flares up a bit, fan your face with it if its hot (he will be too!). Also pretend to have ride-up and pick your knickers out while he's watching, he'll know they're there but he just won't be able to see em! Also try pulling his hair, flicking his forehead, telling him his underwear's showing when its not, or tweaking him you know where. In PE there's a million other ways for a girl to tease a boy, just ask. Hope this helps xx