[bzbarsky]

Just about every single state has state-level funding for schools that acts to even out those disparities.

Worse yet, spending (per pupil) on its own turns out to not be a very good predictor of quality of education. It doesn't even seem to be a great predictor if you control for parents' SES, from what I can see for various school districts in Boston's suburbs.

Put another way, a number of quite distressed school districts spend more than various "good" school districts, with much worse results. DC public schools are a poster child here, but not the only example by any means. So it's not just a matter of funding levels at all.