This is a really cool approach to student learning & self-assessment. Jill uses a calculus example to make her point, but it could easily be applied to almost any other math (or other discipline's) content.
It is a pretty radical departure from where we currently are, though.
To give weaker students recognition, she suggests teaching them a new topic first and then having them present it to the rest of the class. Or asking weaker students to help students in a younger grade.