Oh where to begin...
In grade school, I pulled the chair out from under a (very) obese girl for fun. She fell, cried a lot, I DID ADMIT TO IT (no one would have caught me), but I got suspended for a day anyway.
Also, I got into a fight over a snow mound and I bit a kid. Two days, had to eat lunch with the counselor for a week and talk about my "problems" (we actually talked about dinosaurs... I was seven).
In sixth grade, I drew a very realistic penis on the chalkboard of the teacher's lounge. I got caught leaving the scene of the crime. It was REALLY funny at the time. I became a legend.
In High School, I was in charge of this daily news program. We used stock footage of the SS marching and synced it up to the school's fight song and used it as the opening credits once. We would also routinely use footage of our principal (who no one care for, really), and overdub voices of Stalin, Hitler, etc. Got major-league suspended for that. After Columbine, we toned it down, since we didn't wish to be associated with that sort of thing. BUT, the editing experience was the first time I used a Mac for real work, so it was cool.
I also once, with some friends in HS, wrote a note to a friend of mine (using stolen school letterhead) warning him not to make out with his girlfriend in the hallway or else he would be expelled. We even sent it through the school mail, and cloned the signature of the principal using photoshop. It was a pro job. He got it in second hour, and his facial expression was priceless, since he was the Valedictorian-in-the-making, and took school pretty seriously. Still my favorite prank I pulled. We told him, he got really angry and tried to kick six of our asses at the same time, and we all got suspended. Years later, we're still good friends, and he has it framed on his wall.
As a "senior prank", we stole all of the mouse balls from the downstairs computer labs and mailed them back to the school, with the return address being the principal's home address.
I was never a delinquent, but I sure did love pranks. Most of the rest of society apparently does not, so I toned it down for college, although we did a few from time to time.
Ah, memories...