Here's how this morning's lesson went:
Me: What letter is this?
AJ: "A"... A, A, A
Me: Very good. What letter is this?
AJ: "J"... J, J, J.... Hey, that's my name!
Me: You're right! These letters are on the same block. That's neat... Now this is hard... What letter is this?
AJ: Ummm... I don't know...
Me: It's "U".
AJ: AJ, AJ, AJ
Me: No, no... It's "U'
AJ: AJ, AJ, AJ.
Me: AJ, listen, It's the letter "U".
AJ: AJ, AJ, AJ,
Me: Oh, I get it. Maybe we'll save "U" for a couple of weeks and come back to it...
AJ: Save me where?
Me: Nevermind.

