Some of the final year pranks at our school were funny yet harmless. They put a giant pink papier-mâché elephant in the middle of the tiny school car park. It was even put in the paper. Another year, one lad managed to get hold of some temporary road signs(it was something to do with his dad's job), which all had "Diversion" written on, placing them at strategic points such that following them could never get you to the school (and the majority of the kids had to be driven there).
One of my favourites was in the year before I finished. Our headmistress was really unreasonably strict with uniform. In fact one person was nearly suspended for not taking his blazer to school (yet was still wearing shirt, tie and smart trousers). She said that any people even on their last day not wearing uniform would be sent down to her to be dealt with. So on the last day, all of the final year boys (about 90-100) all turned up in Hawaiian shirts and shorts. It may not sound that funny, but in our school that was ballsy and the reaction on her face when she saw them all come in was fantastic. Ahhh, memories....
I would do feces and acid
