A young man went to a brothel. The lady at the counter asked him what his choice would be.

The man wanted to know what was available.

The Madam said, "On the first floor, we have the ex-models. They are all slinky and sexy. On the second floor, we have our ex-actresses. They are all buxom and beautiful. On the third floor, we have our ex-teachers..."

The man said, "Say no more! Lead me to the third floor."

"Are you sure? I'm surprised that you would prefer ex-teachers to ex-models and ex-actresses."

"It's obvious, ma'am, teachers always make you do a thing over and over again, until you're perfect at it."