I think your teacher stole that from the old joke about the two nuns, sister Mathematic and sister Logic. The joke is like: In the monastery X one of the nuns was very mathematical, therefore she was called sister Mathematic, another one was very logical, therefore she was called sister Logic. One day sister Mathematic and sister Logic were out walking around, a man was running towards them. Sister Mathematic said to her friend: "O dear! Why is he running towards us?" Sister Logic answered: "That's logical my dear, he wants to rape us" "What should we do?" screemed sister Mathematic. "It's logical, we have to run from him" And they started to run, but the man was catching up. "What do we do?" said sister Mathematic. "Well, it's logical" said sister Logic, "He can't folllow us both, therefore we have to split up. Then at least one of us will be safe." And so they did. The man followed sister Logic and sister Mathematic went back safely to the monastery, worrying herself sick for sister Logic, who arrived hours after. Sister Mathematic asked her "What happende?" "It's logical" answered sister Logic. "He caught me up" "And what did he do?" asked sister Mathematic. "He started to take down his trousers" said sister Logic. "And what did you do" said sister Mathematic. "I lifted my skirts" said sister Logic. "And what happened then" whispered sister Mathematic with fear. Sister Logic smiled and said: "I escaped him, of course. It's logical my dear. A woman with her skirts up runs much faster than a man with his trousers down"

And then it ends with the moral of the story, that if you thought it would include sex and/or nudity, you have to pray 10 Pater Noster and 10 Ave Maria