In our town it used to be a competition for muck up day between all the schools, and all of them used to vandalise each other. That was up until a couple of the schools got it banned. Ours still has muck up day, except we can't do anything too drastic..
One of the years they gladwrapped all the walkways and everyone was piling up and falling over, oh the stupidity. And they made all the teachers pay to get into the carpark. A few years back they actually managed to drive one of the teachers cars over to these cement pylon things and they lifted the car on top of them...
And basically, they slash all the P platers tyres, or egg them. Other schools egg ours and toilet paper our sign.