Thanks for the answer. I am not worried at all, just curious about how most teachers would ask kids to play black keys, especially T&A book mentions the "walk up" method.

I don't have music background. I sit in and listen to the lessons and try to remember as much as I can what his teacher said or played. I am also learning along with him. Not that I really want to learn, just try to make practice time a little fun. When he practices, I will remind him what his teacher emphasizes (like curved fingers, downbeat, etc). After that, it's his turn to be the teacher while I play (I should say I try to play. xD).