Sal Khan's thoughts on mastery learning
This idea of mastery learning was always kind of this gold standard. This was actually as a part of a fellowship I had while I was at MIT called the Eleranta fellowship to make a learning software for students with ADHD. It immediately struck a chord with me because going into that, the whole premise of the software that I was working on was this idea that it's not that students aren't capable of learning some advanced mathematics or that the topics are actually difficult. It's more that they just have gaps in their knowledge.
I did a lot of tutoring in high school and I saw that over and over again; the reason why students were having—my friends were having—trouble with algebra, geometry, it was just because they had a gap in their negative numbers or dividing decimals or logarithms or whatever else. Good students start failing algebra all of a sudden and start failing calculus all of a sudden despite being smart, despite having good teachers. It's usually because they had these Swiss cheese gaps that kept building throughout their foundations.
Now, a lot of skeptics might say, "Well hey, this is all great philosophically; this whole idea of mastery-based learning and its connection to mindset—students taking agency over their learning—makes a lot of sense, but, but, but it seems impractical." The real philosophical core of Khan Academy is mastery learning, and everything we've built—whether it's the video library, the articles we have, the 70,000 items, the game mechanics that we have on our site—it's all in service to mastery learners.