Every year (when I was in high school) I used to make industrial-grade crackerballs (the fireworks available back then that exploded with a pop when you threw them down on pavement) out of Potassium Perchlorate and one other ingredient.
The report was cherry-bomb sized, but not as fierce as an M80, and everyone I sold them to knew to either throw them against a wall or hit them with something like a spade. I was busily making them in study hall, wrapping the finished products in tinfoil and putting them in my satchel, when a classmate came over and said “Whatcha doing?” I told him, and he continued to stand there – said he wanted one. I got nervous that the teacher would come over to see why he was out of his chair, hurriedly gave him one with the usual safety lecture.
During my next class I was summoned to the Principal’s office. Apparently, idiot-boy took it to his shop class, put it on an anvil, and dared idiot-boy 2 to hit it with a hammer.
They never did find the hammer head, idiot boy had a bloody nose and no other injury, and the big viewpane glass between the shop instructor’s office and the shop broke.
The Principal asked if I had any “exploding powder”, and I admitted that I did, brightly adding “How much did you want, sir?”. He replied “All of it”.
No suspension, just sent me back to my class.Only time I ever got in trouble at school.