Replying separately to the tutoring anecdotes, you reminded me of someone I tutored who was having trouble learning the chain rule. He got it after going through (with supervision) a single example I assigned - calculate the derivative of sin(sin(sin(sin(sin(x))))). At which point he rather angrily exclaimed "why isn't that example in the book?!"

I'm not quite sure what the connection is, but the combination of

> Easiest tutoring sessions ever when they just needed some quiet space to read.

> A lot of people struggled because HS has so little focus on rote memorization.

brought it back.