kengr

General further response:
In education, at times a teacher is required to use a badly designed curriculum or text. In that case, there is only so much a teacher can do: Their boss, and their budget, mandates what is to be used, and what can be done to upgrade/replace that which might not be working.

This is right up there with jumping around in a textbook: it is best done only carefully, and after ensuring the student has the required information background.
I've done it twice now where that wasn't the case. Both times, I succeeded in spite of the problems made, through massive extra effort.
In one case where (if we were actually using a text) we would have jumped around some, the instructor presented his material in such a way as to be coherent and cohesive in the order of presentation. In that case, though, the instructor has effectively written his own textbook.

Just some thoughts that were inspired by some of the comments.