-come up with different excuses not to do it every lesson. "Girly probs" works particulary well on male teachers, and "my bunions are playing up" is always a classic. go into great detail if possible.
-laugh manically weneva you do something wrong
-in cross country, take the wrong turning, then run away and hide.
-in sprints, turn round and run the other way. carry on running until you can escape and hide.
-in 1500, try and walk it all. say you're just really really unfit.
-scream madly for people to throw the ball to you. hop around alot. when they do, scream and drop it.
-turn up in high heels, a boob tube and a 9 inch weeny skirt.
-if your team is losing, stamp your foot and walk off the pitch shouting "i dont wanna play anymore!"
-turn up in a rival skool's kit.
-go to the oppisite sex's lesson. if the teacher complains, launch into a speech about sexism.
-ogranize a protest rally. try and involve tabards.
-aim javalins/shot putts at the teacher. try and be discreet about it.
-tell the teacher your grandfather played some sport for england. go into great detail. you'll earn their instant respect.