Little Johnny was a constant disruption in his third-grade class due to his loud, frequent flatulence. After keeping him after school, his teacher demanded an explanation for his offensive behavior.
"I do it because I'm the best at it, and I'm proud of that," Johnny declared.
"If I can prove I'm better than you, will you stop?" the teacher challenged.
Johnny agreed. The teacher placed two sheets of paper on the floor, each with an identical pile of chalk dust. Johnny dropped his pants, squatted, and let out a fart that blew away all but a tiny speck of dust.
The teacher then lifted her skirt, removed her panties, squatted, and farted. When she finished, not a single trace of chalk dust remained on her paper.
Astonished, Johnny asked to see it again. As she repeated the feat, he peeked up under her skirt.
"No wonder you won!" he exclaimed indignantly. "You've got a double-barrel!"