Johnny, a 5th grader, came home from school and his mother asks him
what the lesson was that day.

“Sex,” he replied.

“We didn’t study that subject till I was a senior in High School, ”
said his mother. “For lying to me you can go up to your room and stay
there.”

His older sister gets back from school shortly after that time and her
mother mentions this to her.

Her daughter comes back with, “Johnny wasn’t lying. When I was in 5th
grade we had a lesson on sex education. Things have changed since you
were in school.”

Chastened, his Mom said, “I’ll have to apologize to Johnny.” She goes
up to his room and, through the partially open door, sees him
masturbating.

“When you’re through with your homework, you can come down for supper,”
she tells him.