I've worked through Geometry, Algebra I and Algebra II on my way to Pre-Calculus and Calculus, and I've noticed that the one weakness of Khan Academy is the lack of a text book. I basically had to write my own, deducing the needed principles, rules or problem-solving steps. Several times I printed summary content from other Websites.
People like me would benefit from more "videos" that are text-only and clearly state the step-by-step mechanics of working certain problems, provide formulas or list rules.
I discovered that the best guides are buried in the Hints sections, which I often transcribed verbatim.
Otherwise, I think Khan Academy is fantastic.
I'm age 70 and trying to compensate for the woefully deficient math teaching I had during my first 13 years of formal schooling.