Ours was the day AFTER our grad ceremony, so I already had a little piece of paper and was ready to unleash...
Champagne brekky (attended by a few of the cooler teachers as well

) kicked off proceedings, walked into the CBD as a group, I remember three things from the "before we got to school part":
Large group dancing on various roundabouts...
Getting stuck in an elevator because all the guys in there were jumping around and it caused a problem with the elevator...
Our entire year level in the "foyer" of the local police station singing...
When we got to school, the principal told us we had an alloted time to be at the school, and were confined to a certain area...
Needless to say, a handful of us rocked into a year 8 class, where I sat on a young girl, as the others gave the year 8's a lecture about respecting authority, wasn't part of the principal's plans...
At one point we had a couple of teachers tied up...

and water bombed...
I didn't take part in the "get filthy" throwing around of fish guts, manure, etc, as I was too busy having beers with one of the cool teachers in a deserted classroom

Still catch up with him to this day!
I can say that 2005 (my year 12) WAS the last time that any type of muck up was allowed at the school...