Also, as background, I guess I should say that this is an elementary school covering pre-k through 5 and that they use TERC. The principal thinks that by grade three, there isn't a big range in math ability, and that students learn so much conceptually by using the TERC lesson plans, that even if they know how to perform the "arithmetic," they are still missing important math learning by not getting the conceptual TERC lesson.
So, given the principal's mindset, I think I might have a greater probability of success if I propose that the pace of class would be speeded up by covering the concept with the on-grade TERC lesson, and then moving on to the TERC lesson for the same concept the next grade up. For example, students learn two-figure addition, and then move right into three-figure addition.
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