Thanks for the link, Bostonian. I'll have to look it over.

My comment was based on what I know of instructional levels in other industrialized nations (not comprehensive, by any means), not so much the achievement outcomes of said instruction. (Though that has its own twists.) Since the question has to do with grade-levels-ahead, I wanted to introduce into the discussion the scope and sequence of math instruction in specific communities, and their alignment with grade levels. I could have rephrased it as, elementary and secondary math instruction in most of North America appears to be about 1-2 years behind instruction in much of the rest of the first and second world, therefore, our concept of grade-levels-ahead may be accordingly shifted.

...pronounced like the long vowel and first letter of the alphabet...