"Skipping Grades" joke

A first grade teacher was having a lot of trouble with one of her students. "What is wrong with you, Billy?" she asked.
"I'm way to smart for grade one," Billy answered. "My big sister is in grade three and I'm smarter than she is. I think I should be in grade three too!"
Having had enough, the teacher took Billy to the principal and explained the situation to him while Billy waited outside the office. The principal told the teacher he would give Billy a test and if he failed any of the questions, then he was to go back to grade one and behave. Billy was brought into the office, the condtions were explained to him and he agreed to take the test.
Principal: "What is 3 x 3?"
Billy: "9"
Principal: "What is 6 x 6?"
Billy: "36"
And so it went with every question the principal felt a third grader should know. He then looked at the teacher and said, "I feel Billy can go to the third grade."
"May I ask him some questions?" the teacher asked the principal. The principal talked it over with Billy and they both agreed.
The teacher asked, "What does a cow have four of that I only have two of?
Billy thought for a moment and then replied, "Legs."
"Ok, Billy, what is in your pants that you have but I do not have?" asked the teacher.
The principal was shocked with the question, but before he could stop him, Billy answered, "Pockets."
As he breathed a huge sigh of relief, the principal looked at the teacher and said, "Put Billy in the fifth grade. I missed the last two questions myself."