Why don't we hand-tailor a bespoke educational curriculum and methods for each student? Primarily, it's a cost issue; secondarily, it's an aptitude issue for the educators. (My parents were both in public education, and some of what I saw as a user and what they reported as members was utterly appalling.)
But, it's the cost issue that makes it a total non-starter. Very few school districts will, across the board, be able to afford the teacher:student ratios required by individualized, customized instruction processes for each student.
If they could not afford to do custom-tailored program for average student, why should they do it for gifted? Results of the survey shows that gifted kids do alright in life, make more than average, get Ph.Ds, etc. Should schools (and average Joe who pays for it) provide them with even more advantages?
Why should we tailor our educational processes for the non-gifted end of the spectrum or those with behavioral difficulties?
My answer is that we've decided to make larger per capita investments in "outlier" individuals and the vast middle of the distribution population is accommodated with a standardized curriculum. I'm OK with that, though I'm concerned that we concentrate disproportionate resources on the left side of the distribution without investing enough on the right side.
I don't view the problem as "How should we use our limited resources to most effectively level the playing field?" but rather "How should we use our limited resources to most effectively foster the development of our future society?" It's no surprise that those two fitness functions result in different choices.
Best and brightest at 8-15 usually do not end up best and brightest in later career. You can see it even in the fact that average salary of that cohort is only 80k/year - only slightly better than average for ALL college graduates. None of those geniuses are particularly impressive and most ended up doing the same work with the same quality as the rest of us.
There was research that showed that IQ after 120 stops being correlated with success - other factors start being more important.
Yeah, my supervisor for my undergrad thesis is a brilliant researcher who's still publishing good work 20+ years into his career. He was just a normal dude in undergrad who started in engineering but switched to math because he disliked project management, and he certainly wasn't in any sort of "young genius" program through grade school. But his PhD thesis was runner-up for best in the country, he consistently presents at all the major conferences in his field, and he has even won a few teaching awards.
It's not about what those individuals deserve, it's about the societal return on the investment of their education. The potential return is simply greater.
But, it's the cost issue that makes it a total non-starter. Very few school districts will, across the board, be able to afford the teacher:student ratios required by individualized, customized instruction processes for each student.