Heh. Since we are into high school stories, here’s mine:
My HS shop elective was electronics. They taught us how to do basic TV repair (back when their were picture tubes and things you could repair).
The teacher taught us the proper safety procedure for measuring the plate voltage: one hand behind your back, carefully slip the probe tip under the rubber hood, take the reading. Lots of warnings and horror stories (“The most common injuries aren’t actually from the electricity but from your muscles contracting and yanking your hand out of the enclosed space, cutting yourself open on anything nearby”).
My turn comes. TV on the bench against a cinderblock wall, back removed, power on. Heart in hand, I very carefully sneak the tip under the hood ... and at that exact instant, the freaking FIRE ALARM went off, with, of course, the klaxon about 18 inches above eye level on the very cinderblock wall I was facing.
(Laugh) To this day, the worst jump scare I’ve ever had. Everyone swore up and down it was a scheduled drill triggered from the office, but I never quite believed them.