You know what was a better day? Being the kid that your teacher had the library train how to run the AV equipment. Then, said kid gets the projector and sets it up to run for the class. Then, when running the film and "monitoring" the projector to make sure everything is "OK," said kid takes a felt tip pen and presses it to the film coming off the front reel so that on the screen, said kid and said kid's friends "in the know" see the squiggly ink line projected on the screen and said kid and said kid's friends "in the know" all get a big kick out of it... allegedly.
You left off the most iconic trick: As the film is playing and moving to the take-up reel, load it with spitballs by placing them one at a time directly onto the film just as it gets to that reel. Usually a couple of hundred or so work just fine, and keeps the '
spitball workers' limited to just a couple seated on both sides of the projector. Busy making and planting(loading) the film with slobbery wads of paper takes a surprising amount of coordination and focus so only the brighter troublemakers were qualified.
Once the film is over and it's time to rewind the film back onto the primary reel....in high speed
. It always started slowly at first but towards the end of the rewind, that thing is flying---throwing little wads of paper and moisture all over the room at projectile speed.
It was glorious.
We....er, they never got caught.