Child's play (Driving license is like a report card)

A mom is driving a little girl to her friends house for a play date.
"Mommy," the little girl asks, "how old are you?"
The mother looks over at the little girl, "Honey, you are not supposed to ask a lady her age, it isn't polite."
"OK," the little girl says, "How much do you weigh?"
"Now really," the mother says, "these are personal questions and are really none of your business."
Undaunted, the little girl asks, "Why did you and daddy get a divorce"
"That is enough!" the exasperated mother exclaimed and walks away as the two friends begin to play.
"My mom wouldn't tell me anything," the little girl says to her friend.
"Well," said the friend, "all you need to do is to look at her driver's license. It is like a report card, it has everything on it."
Later that night, the little girl says to her mother, "I know how old you are, you are 32."
The mother is suprised and asks, "How did you find that out?"
"I also know that you weigh 140 pounds."
"How in heavens name did you find that out?"
The little girl continues on triumphantly, "And I know why you and daddy got a divorce."
"Oh, really, why?" the mother asks.
To which the girl replies, "Because you got an F in Sex."