Pace learning by understanding, not by the calendar: mastery before moving on

In many classrooms the pace is set by the calendar: the unit ends on Friday, so the class moves on, whether or not everyone has understood. Students who missed a step carry the gap forward, and later topics that rest on it become harder, which is why some students feel they are "bad at maths" when they simply missed an early idea.

Mastery learning is an approach in which students must show they have understood a topic, usually to a high standard, before moving to the next, with extra help and further attempts available until they do. Sal Khan's talk "Let's teach for mastery, not test scores" is a well-known case for it. Benjamin Bloom's finding, often called the 2 sigma problem, that one-to-one tutoring with mastery methods produced much better results than ordinary classes, is the reason many people want to make this approach practical at scale.

The real objection is logistics: a teacher with thirty students cannot run thirty different paces. Technology and peer help may assist, but time and training are needed.

What would change our mind: large, careful trials in which mastery approaches do not beat ordinary teaching.