Some advice handed down to me by two academics I had the fortune of interacting with in graduate school:
1) From one of my Ph.D. advisors who was Korean and specialized in econometrics (and with whom I published some scholarly articles on econometrics when I was fiddling around in that career): To maximize your son’s ability to learn math, get him into the habit of making written copies of what he should remember. Because, as that math-geeky econometrics professor said to each of his graduate students in first semester course in his subject, “The hand will remember what the eye will forget”. I later used that method to recall the significant findings of over 150 research papers, all organized within various topics in the major, when taking (and acing) my second-year comprehensive exam.
2) From Eugene Fama (use the Google machine to learn his credentials), who once guest-lectured my class of grad school cohorts one semester when in town giving a presentation on a working paper: When reading math terms, equations, etc., in a problem, equation, text, remember that math is a language and say every symbol as a word, as well as all of the terms and numbers shown with it. Don’t just look at it and skip pronouncing it, even if only in your head. That vastly improves one’s ability to comprehend what the math symbols are intended to communicate.