Note: I have already touched on these issues in a much longer, much broader post on education and on twitter at some length, however I thought it’d be useful to zoom in on this issue and marshal the evidence in one place for future reference.
It is still commonly supposed by much of the public that school funding is terribly unequal due to reliance on local funding mechanisms (especially property tax). Although there were once modest inequalities associated with local income levels (several decades earlier), this information is generally wildly out of date today. Within the vast majority of states districts with less advantaged students (read: higher poverty, lower income, fewer parents with college degrees, minority, etc) actually spend at least as much money per pupil (often more), both overall and in the narrower instructional expenditure category, and where there are inequalities these differences are usually quite modest and fleeting.
Though school funding is still significantly a local affair in most states there is substantial progressive redistribution of state and federal funds that effectively offset these potential inequalities (and then some). Some districts may choose to spend more controlling for income/wealth (tax effort) and there is some variance (mostly poorly explained by any SES measure), so that malcontents can always find isolated examples to complain about, but various formulas employed at the state and federal level sets a floor and effectively acts to prevent there being substantial positive correlations between school spending and district median income (or low poverty rates, percent minority, school free lunch percentage, and so on …. this holds across multiple measures).