I would argue pretty intensely for taking any reference material out of students' hands (I mean, did you you miss the fact that the site was titled DOING mathematics?!?). I wonder, however, if there is space for helping teachers learn to use textbooks that already exist as a launching point for creating their own quality instructional materials? This, I hope, is the beginning of a post "series" about infusing "doing" into existing curriculum.
"Ok class, turn to page 900 (because there are way too many pages of reference and practice problems) and find the section on "Exponential Growth:"
We will be exploring global population until (insert date and time here).
WHAT WILL THE GLOBAL POPULATION BE AT THAT EXACT TIME?
The point here is that NONE of the reference material is present...at all! Students don't need a definition for exponential growth until they want one to verbalize what they are noticing about how population grows. They don't need variables and models until they introduce/create them themselves to describe the patters they see in that growth. They need to create this for themselves, not learn how someone else does it. The beauty here is that students will create their own models and we can discuss the benefits and pitfalls of each.
This simple redesign, or infusion, is a simple recreation of what already existed in a reference text. We can teach/trust teachers to create this experience for their classes without putting the reference text in the hands of every student (or trying to create a curriculum that is widely distributable). Of course, even with the "infusion" a lot of harm can still be done in how we help guide students in creating their own model...but that is a topic for a later post.