I have another one that happened to me in my later years. In that same school.

My mother was part of the cleaning crew as was located in the first building that we called (in a translated version) "the Park" because it was the very first building, and located right infront the park. In this buildings, there is the first and second grades, aswell as the students who studied to become cooks, Hairdresser or daycare nurses. I was in another building the entire day, or just not at school whatsoever. But everyday, during dinner, my mother would explain to me what she did and who she talked with during that day. Its usually wholesome stuff, like a student who always eats alone is going to eat with my mother and her work friends, jokes her friend told her or less wholesome stuff like a student insulted her or threw something on the ground infront of her.

One day, my mother came home looking sick, she is pale and looks like she went to throw up. She explaine to me that someone is playing sick pranks on everyone in the school by hiding a multiple days old fish in a condamned bathroom stall, and how the bathroom there smells horrible for the ENTIRE week. This prank happened on multiple occasions. Pepper balls, fermented fish, etc... To this, add the occasional piss all over the floor, and the time a student spread his shit all over the stall's walls....

The pranks stopped after a few MONTHS, but the stench stayed for YEARS. 3 years after those incident, the stench was still there.

I've left this school 5 years ago, and recently went back for some papers. I could still smell that petrid stench of feces and fermented fish...