Sex education class
 

One day a boy came home from school and his mother asked, "What did you do today, son?" The boy replied, "I learned a lot in Sex Education class." The mother, thinking this to be a dirty joke, yelled at him and sent him to his room. Later that day, the daughter comes home and the mother says to her, "You'll never guess what! Your brother told me he learned a lot in Sex Education class! I sent him to his room!" "Mom," the girl said, "he really does go to a sex education class. He wasn't lying" The mother, feeling very badly about the mixup, goes to the boy's room to apologize. She opens the door to find him masturbating and she says, "When you are done with your homework, come out here, we have to talk."