The firework was lit and tossed into one of the steel barrels used as garbage containers on campus. The two walked down the hall, noted the several seconds of absolute silence which settled over campus following the blast, and walked into the classroom of a teacher they both had, which was generally open during lunch. The teacher looked at both of them, shook his head and said, "Gentlemen..." with a slight smile.
One of the students retyped spirit copier forms (this was several decades ago) for a teacher following lunch. The typewriter used sat in the vestibule to the principle's office. He listened that hour while the yard patrol supervisor and secretary discussed "the bomb" which had gone off, as the faint smell of burned garbage wafted through the building. That day's work had more than the usual share of errors.
Nothing more ever came of it.
My, how the world has changed.