This teacher is teaching her grade four class, and she's telling them that the word of the day is 'Contagious.'
She asks if anyone can use this word in a sentence, and several people stick up their hands. "Carl," she says.
Carl says, "My dad told me to stay away from kids with mumps, beause they're contagious."
"Very good," says the teacher.
Then she picks Suzie, who says, "The atmosphere was contagious," and the teacher says, "Excellent, Suzie!"
Then she notices that little Johnny has his hand up, at the back of the class.
"Yes, Johnny?" she says.
Johnny says, "The other day, me and my dad's a-sittin around, and we saw our blonde neighbour painting her fence. She had a tiny little model car paint brush, and she was going in tiny little strokes up and down the fence, and my dad says to me, "Jesus, it's gonna take that cunt ages to finish that fence."