High school brings so many memories.
I had a math teacher who was chalk drawing graphs on the walls if it didn't fit on the green board.
He said, I'm not adjusting this shit now.
Crazy schoolmates also used chalk for other purposes, such as staining girls jeans and then asking if they can clean it up. Ass was of course the main target.
One hot day in may we were throwing water baloons out of the 3rd floor window landing in front of school entrance, almost hitting few people on the head
The fun didn't last long as one furious teacher came into our class and send us down to clean up the mess.
I remember two funny tricks from high school. Somebody started the habit of putting pins on others chairs. Yes, I sat a couple of times on a pin but soon I learned to check the chair before sitting. I was probably the one who most often managed to avoid sitting on a pin. But I remember a guy who sat lazily on his seat and suddenly jumped up and shouted loudly "Oh fuck!". And there was another guy who always sat on his leg in the chair. Of course, leg protected his ass but he once had a pin in his knee.
But my favourite prank was this: We adjusted the timer of radio in our class so that it starts to play during the lesson. Accidentally, it was during the time when last-year students were having their last days, and they were often clowning in the school radio in their last week. Well, during the lesson, the radio "surprisingly" started to play some heavy metal. And our teacher, who was also the headmaster, thought it's last-year students clowning. But then he realised the music comes from the classroom's own radio, not from the school radio. Then he started to ask which one of us has the remote controller which, of course, we didn't have, we just used the timer. Well, he just turned of the radio and continued the lesson without blaming us for interrupting. He was a nice and funny guy.
And of course, we had also fingered the locks of doors so that they were more difficult to open. Probably all teachers knew it was done by us but they really didn't care.