My mother used to tell this one about her father, my grandfather, John “Hicks” Connelly.
Hicks was a math teacher par excellence, who taught both at Loyola University Chicago and Loyola Academy, which was for years on the Loyola campus. He was a no-nonsense kind of teacher, tough but fair, and didn’t put up with adolescent hijinks, not even from his oldest grandson, who’s named after him. (I speak from experience.)
He usually came home in a pretty good mood (my aunts and uncle can correct me if they wish), but this one day, he got home sullen and didn’t want to talk. My grandmother, Walkie (real name: Genevieve, nickname: Wally, called Walkie by her oldest grandson), finally sat him down and said, “John, something’s bothering you. Please tell me what it is. Did something happen at school?” And he told this story:
It seems that he walked into his classroom and, as he usually did, put his foot up on the chair. He noticed that a few of his students were giggling and pointing, and assumed there was something on the board behind him. “Knock it off!” he ordered, and for the entire period (which I think would have been 55 minutes in those days) taught the class standing with his foot up on the chair, never turning around to look at the board.
The period ended, and the boys filed out of the room. The last young man to leave the room stopped at his desk. “Mr. Connelly, your fly is open.”
Walkie, who had a tremendous sense of humor, busted out laughing, and when my mother (who was in high school, I think) got home, Walkie made him tell her the story. I think he finally saw the humor in it.
from The Sound of One Hand Typing