A teacher and little Johnny

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"