N=1 anecdote, but I'd say your thesis is not only wrong, it is diametrically opposed to reality. Having seen both, crumbling local public school[0] and gifted state run boarding school[1] your story of the 'smart' kids setting an example never happened. Mostly, I think, because you underestimate just how far ahead they are. It's not a case of "things come easier"; it's "skip every class and show up on the last day and still out perform everyone else". As an aside, I learned more from my peers and participated more in the community when we had a shared foundation to work with.

What you're advocating is a deeply lonely (and I'd argue psychologically damaging) experience and it really bothers me to see so many people in this thread want more people to experience it.

[0]https://en.wikipedia.org/wiki/Wilson_High_School_(Florence,_... [1]https://en.wikipedia.org/wiki/South_Carolina_Governor's_Scho...