See Igros Moshe re cheating on Regents exams and apply to the first posting in this thread.
I really hope you don’t do such things!
Something that doesn’t hurt anyone is one thing. The story goes that one year the girls strung up fishing line from the ceiling and attached funny hats to the fishing lines. So, when the teacher walked in, the girls were wearing the hats – and when they sat down, the hats remained hanging.
That doesn’t hurt anyone. But a lot of the other pranks are really wrong, immature, mean, cruel, etc. etc. etc. etc.
(Just a side note – if you ever heard of game, Truth or Dare, I think it’s a similar concept of something that is terribly mean.)