One day, when Johnnie came home from school, his mom asked him how his day went.
He said, "We're learning about sexual education."
She smiled, and said, "At least he's learning something useful."
Johnnie went up to his room. A little later, Johnnie's mom went up to his room to call him for dinner. She opens his door and sees him playing with himself.
She says, "Johnnie, when you're done with your homework, supper's on the table."