[papertyger]

There is no logic in the manner of some of the groupings unless you know higher math.

That's the point.

It won't be "higher" math, anymore.

To borrow from your own example, how many FReepers have any more than a vague idea (including myself) to what you're referring?

[prof.h.mandingo]

My reference was in building a foundation in order to apply more advanced concepts. Cart before the horse. I can’t make it much simpler.
You cannot teach a young child concepts held in multiplication before you teach adding and subtraction.
Rote memorization works. It’s that simple.
Are you saying that Common Core is actually good??? Common Core goes against what we know of child development. As a teacher I can confirm how much this is hated by most teachers.