Can you tell me how to cause trouble in school, without getting in trouble myself? :)

Clogging up toilets&taps. Shoot rubber bands at the teacher when he/she is turned around. Laser pointer pens are amazing to annoy teachers. Hide your phone and let someone ring it.

Be creative, you'll find something insane to do one day

My friend would go to 2 different first years and tell them that the other person has said something about their family. The first years don't even know each other and they end up fighting=)

HAHA! Open up a milk container and go to the bathroom (lift up roof and place it down) or locker, put the milk in there and let it rot. I done that at my school and evacuated the building=)

Put the fire alarm on. Ive done that a few times to waste lesson time especially in maths