When I was in year 11 the year 12's of that year stuffed muck up day up for us because they went too far (according to the Principal anyway), well maybe not that far after reading some of the idea's above. But Anyway they rocked up at the School at about 1 am the morning before muck up day, armed with a caulking gun & a carton of liquid nail canisters, and procedded to fill up every lock in the school they could find with liquid nails!! they got more than half the school done before they were disturbed!! ( And it was a pretty big school!) I remember rocking up to school that day to see a fleet of locksmiths in the car park, most of those locksmiths spend a good couple of days fixing them all.