Counting

A teacher asked little Johnny if he knows his 1 to 10 well
"Yes! Of course! My pop taught me...even more than 10"
"Good. What comes after three?”
"Four," answers the boy.
"What comes after six?"
"Seven."
"Very good," says the teacher. "Your erm...dad did a good job. Now...so what comes after...lets say ten?"
"A jack"