Worst prank you played in school.

[sulavaca]

I just remembered one from years back, but it turned out to be quite a big deal in the end, even though we didn't think much of it at the time.
We used to skulk off to the broom cupboard to skive our German class at times. One day, near the end of term my good mate decided it would be fun to record over one of the disused German language cassette tapes with a lot or lurid sexual innuendoes and language. He even went as far as inviting folks (listeners of this tape) to his house [address included] for some unadulterated pleasure.

A few weeks later his parents were called to school.

Unfortunately, it transpired that this "blank" German language tape happened to have the verbal GCSE language questions recorded onto it originally and was subsequently played to a class.

Ooops!

Okay, not so much an intentional prank, but funny never the less. I hope he isn't reading this. He'll likely get a flush!

[Steviebike]

I have many

Once, whilst in detention with some other reprobates another pupil was added to our detention room. The teacher who we called Mrs Teradactyl asked the pupil to make her a cup of tea while she fetched something from another room. We took it upon ourselves to help the pupil by adding washing up liquid to the water of the kettle. It's still makes me laugh to this day thinking of the explosion the water spat out of that kettle and reached the ceiling 8-10ft above!!! Like some hot spring geyser. Amazing. The pupil got an absolute bollocking for being so dim to let us added fairy liquid to the kettle, we got more detention and she never got her cup of tea.

[sulavaca]

It doesn't count as being at school, as I was at my classmate's house. i took over just four tall tins of beer, and knowing it wasn't a lot, we down'ed two each in seconds. So after becoming just a bit drunk, I somehow persuaded my friend to cook up a couple of tins of baked beans, as I was peckish. He did so, just before I then persuaded him that it was a good idea to add half a bottle of peppermint essence, a few drops of blue food colouring, and then from his loft window, pour it down the side of his neighbor's house.
Don't ask me how this all made sense at the time. I was fifteen.
Anyway he told me the following week that he somehow got into trouble. And there was I wondering how anyone could possibly know it was us.?!?!?!

I think I thought I was invincible when I was fifteen. I'm now dreading my own son becoming that age!