Your link is to a very controversial polemic which IMO sets up a straw man, and then makes its own argument in a (both theoretically and empirically) questionab

Your link is to a very controversial polemic which IMO sets up a straw man, and then makes its own argument in a (both theoretically and empirically) questionable way, based on the authors’ pet “cognitive load” theory (which I personally think is bunk, but YMMV). It should be read in the context of its critics, and taken with a heap of salt. To understand the problem with US-style mathematics pedagogy, I would recommend reading http://www.de.ufpe.br/~toom/travel/sweden05/WP-SWEDEN-NEW.pdf http://www.de.ufpe.br/~toom/travel/sweden05/WP-SWEDEN-NEW.pd... For some advice and materials based on an alternative theoretical framework, let me recommend https://www.map.mathshell.org/trumath.php https://www.map.mathshell.org/trumath.php * * * I think Khan Academy should be thought of as a consistently average-quality US-high-school-style lecture, combined with US-style trivial exercises. It is a slow, unimaginative, pedantic curriculum. But it has the advantages of being free, always available, and self-paced (in the sense that students can keep going through as much of it as they want without needing to wait, and can return to previous sections any time). I’m glad it exists, because it sets a quality floor; live teachers have variable quality, and while many are better than KA lectures, some are certainly worse.