you wrote
What, exactly, happens when you flush an M-80 (lit) down the toilet?

Well if you did it in catholic grade school; like me and Benny "the geek" did
you got "15 of the best" from sister Dorthey Joseph after school with
trousers down; She was a stick-ler on getting her point across more
effectively to the seat of the problem. I t was an effective form of
counciling for 8 yr olds sporting "pompadors" and black engineer boots.

Today I  guess now you get qualified counciling; and testing and if your
clever enough you can make a full time job out of it; and who knows write a
book and get on Jerry Springer.