Let me know if you intend to become a student of mine and I'll start working on that right away.

[Lavi likes goading people into guessing games, doesn't he? He must be used to being the smartest one in any room.]

... and if someone is too old for a gold star, then they're old enough that the punishment for not paying attention is that they don't learn.

[Corporal punishment just isn't his kind of thing. Violence is for people he plans to kill, people who give him no choice, or (usually) those who fit into both categories. When it comes to teaching lessons, obvious disappointment is all the negative consequence he needs.]