Mastery-based learning is good, but there is a degenerate path that is important to avoid. Some students can master basic computational tasks (like addition an

Mastery-based learning is good, but there is a degenerate path that is important to avoid. Some students can master basic computational tasks (like addition and multiplication), but don't have the maturity to reliably produce that mastery; in other words, they're sloppy. A human instructor teaching to the mastery approach will move on with them, and when they are learning a later skill and they make a basic error (7+4=12, for example), will point it out to the student, and let them fix that, and show that they have mastered the more advanced skill. A computer, on the other hand, will just decree that they got the question wrong, have not achieved mastery, and force them to repeat the instruction. It's very demotivating, and still not fully solved, although Khan Academy's recent change allowing students to reset/start-over tests without completing them has helped.