In 9th grade, I used to torture our poor band director. Our band room used to have a hugely long display case with about 20 bust heads of famous composers - Mozart, Bach, Beethoven, Holst, etc. One day, I stayed late after school and took some jump rope from the gym. I then fashioned about two dozen hanging nooses and got to work! Wasn’t the greatest prank, but it was a memorable visual of 20 hanging composer heads - and the stunned, ashen look on our director’s face as he entered the band room.
We used to put a string of fire-crackers in the school court yard with a cigarette “delayed fuse”. Always fun to be 5-10 minutes into class waiting for it to go off and rushing to the windows with everyone else to see what happened!
Two older kids were always getting in trouble. Their best prank was one guy holding a pair of cowboy boots outside the third story window - like he was holding somebody upside down. His buddy was down in the courtyard yelling “don’t drop me!” When the teacher came in the kid at the window quickly dropped the boots and slammed the window like “Nothing to see here!”
By the time the teacher gets to the window the other kid is sprawled out on the ground below!
Those two kids were kicked out of school for good when they had a dirt-bike race inside the school. Up and down stairs, etc.