Here’s a little thought experiment for anyone trying to help other people learn.

Suppose that you suddenly developed the power to predict exactly how long it takes anyone to learn anything. If you’re a teacher, you would know with certainty the different learning times for all of your students and for every lesson. Armed with your newfound clairvoyance, would it make any sense for you to put every student on the same fixed time table if your goal is to make sure that all of your students learn every lesson?

I often say, “Nobody knows ahead of time how long it takes anyone to learn anything.” But if “I know exactly how long it takes anyone to learn anything”, the consequences are largely the same. In both cases, giving students enough time to learn is the only sane thing to do.