I've been using Khan Academy for a few months to upgrade my skills before applying to grad school, as I missed some calculus, stats, and economics courses in my undergrad. I really like that Khan Academy is helping me to understand the concepts and build my knowledge and skills, without having to pay hundreds of dollars for upgrading courses. The caveat here is that this is purely for knowledge, and no credits are available (but pairing Khan Academy for learning with Sophia or StraighterLine speed-runs to get transfer credits may be a good wallet-friendly route). So far, I only have two quibbles: first, the "Get Ready for College Calculus" is mainly a path cobbled together from modules that, in their normal places, flow together, but assembled in such a way that occasionally a quiz will test something whose module wasn't included. Second, I haven't found any way to download my learning history or any proof of my skills (so I may end up doing a speed-run through a paid, accredited platform anyway). I give Khan Academy four stars for being a solid learning platform, and if the upskilling helps get me into my chosen grad school program, I'll definitely bump this rating to five stars.
