In 6th form
there were a couple of lads who were kind of geeky, but in a more eccentric way that would have labelled them as insane if they weren't kids of middle class families. They were decent enough, but obviously didn't think in the same way as most people, so were prone to saying odd things or doing things for their own amusement (such as training themselves to speak and write backwards, including maintaining the original intonation), regardless of it was funny or appropriate for their age.

The best thing they did (of that I actually witnessed) was produce about half a dozen misspelled notes, written in felt tip on A4 paper saying things along the lines of "OuT of Orda, dnt UsE!!!" (actual spelling of these notes is lost to history) and they proceded to stick them on things which couldn't be out of order, such as chairs, bins and doors, including the one to the staff room.

They then, from their seats in the common room, laughed as people would go to put their rubbish in a bin, read the sign and then go and find a different bin to use, or avoid a fully functional chair in the common room for a week.

The staff caught on quickly and the cleaners disposed of as many signs as they could find, but before long they had branched out, and these notes appeared in classrooms and even into lower school, before they got bored and found something else to do.

It was entertaining in a very low key way.
(Nikkusama, Fri 30 Jan 2009, 13:50, Reply)