After his daughter went back to an American school did she become his “son”?
Years ago, there was a fantastic series of books called Core Knowledge. Books the size of textbooks, further sub-divided by subject: ex. Math, History, etc.
Titles: What Every First Grader Should Know; What Every Second Grader Should Know, etc.
It was a VERY rigorous curriculum. Many parents used these books to supplement their children’s education even then, decades ago.
(I don’t know if they are still in print and available.)