I've certainly thought of this before. Weighing heavily against this suggestion is the sheer size of my sample. If what you say is possible, and considering that students are socially promoted, we would have seen some evidence. I mean, nothing stops a student from not getting arithmetic and then going on to be successful with algebra. I started the study looking for such anomalies.
On Nov 2, 2012, at 2:06 AM, Louis Talman <firstname.lastname@example.org> wrote:
> Your "natural progression" completely ignores a significant possibility: The primacy of arithmetic is simply an artifact of a curriculum that denies entry to those who haven't acquired proficiency at arithmetic.