I'm a... victim, I guess... of this mindset. I didn't really start getting even a half decent mathematics or science education until college. If I didn't pick up programming as a hobby, IDK where I would be right now. Probably nowhere good, financially and perhaps otherwise. (Mind you, AFAICT private schools aren't typically much better, and there's less accountability and more personal cost to boot.)

I'm very conscious of what you're saying here and mostly agree with the negative effect of affluent people opting out of the education system. So I'll commit myself to improving the systems that my own kids would be in if I didn't have the time and money for alternatives. But I'm still unsure whether I'll actually send my own children to public schools. The cost to them will be real.