The scales used on global measures of education are scored in a way that makes a few low scores a lot more influential than a few high scores (since the average score on the test is around 70%, it takes more than 3 100% scores to balance out one 0%). So countries which are more homogenous (so that their upper end's scores don't get capped at 100%) and don't have as big of a low class do well, such as Japan, Korea, and Finland.
If the tests were structured so that the average score was 10 out of 100, one genius who scored 100 would be worth 9 people who scored zero.
I think this is a more realistic way to score education; would you rather have the median of the population go from grade level 7 algebra, to grade level 7.1? or would you rather have 20% more utter geniuses in your society? Both have value, obviously, but breakthroughs are made at the edges, and only need to be made once.
All this is to say that we should focus on where the returns are greatest.
In terms of intellect, I'd think that the returns to society from state schooling are greatest from educating the bottom 95%, as the geniuses tend to be more auto-didactic anyway and usually need more in the way of social support and access to academics rather than traditional school teaching. A society that reserves high quality education only for those children already considered to be intelligent, is a pretty stupid one in my opinion.
Also, high quality education is not the same as teaching advanced courses, although obviously advanced courses should be taught to a high quality. High quality education is about the ability to bring standards up across the board, not just the production of geniuses, which educators largely can't take credit for anyway.
If the tests were structured so that the average score was 10 out of 100, one genius who scored 100 would be worth 9 people who scored zero.
I think this is a more realistic way to score education; would you rather have the median of the population go from grade level 7 algebra, to grade level 7.1? or would you rather have 20% more utter geniuses in your society? Both have value, obviously, but breakthroughs are made at the edges, and only need to be made once.
All this is to say that we should focus on where the returns are greatest.