The countries that perform well on international standardized tests generally spend much less money per student, but a teaching job is much more prestigious tha

The countries that perform well on international standardized tests generally spend much less money per student, but a teaching job is much more prestigious than it is in the U.S. I personally think that explanation fits both the "cost is orthogonal to education quality" argument of the parent, and your point that elite private schools have significantly better education quality, though I do not know offhand of studies about this.