Hm I think I have quite a few actually. It were the goods days, as I never laughed as much as back then. I'll give you two examples:
- Back in the days when I went to school (read: oldskool

) we had obliged study hours at the end of every day. That means when lessons are finished everyone goes a very big room and studies for 1h30 minutes... These times were often quite annoying as they were extremely boring to some people. Luckily sometimes there happened some things that spiced things up a bit.
On wednesdays there is a local market near and one student had the brightest idea to go buy a bird, yes, a bird... none of the others had a clue when he released the bird in the big room during study time. So the bird went flying back and forth in the huge room, sometimes sitting on ceiling bars etc... The supervisor just reacted by keep it quiet, etc... Of course half of the people already noticed and started looking to the bird instead of studying... Things became really hilarious when the poor animal started doing his nasty business on our books

"Sir! a bird just pooped on my book!"
- Example two, between two classes as we were waiting for the other teacher to arrive, things were always crazy as usual, you had papers flying arround, some fighting, some went for a smoke (while not allowed), etc... Now two particular guys found it funny to start throwing the wipers of the chalkboard to eachother. Of course these wipers contain white dust of the chalk used on the board so not very much later things got messy. Anyhow, as at a certain point I looked and I saw teacher arriving in hallways and at the same time I saw one of the wiper flying through the air in that direction. I was like "ohoh this is not going to end well" and well teacher had pretty white face and afterwards pretty red one...
I got dozens of others but heh...