Do you not know that the US is a Federal system and there are (at minimum) 50 different ways that schools are funded?
California's schools (for instance) aren't funded by local taxes, they're funded by the state and allocated funding based on a formula[1] of performance, need, population, etc. They can be augmented by local taxes, but in practice that's rare as the wealthy just avoid the system altogether; instead, opting for private institutions.
That's at least 12% of the population that is not funded in the manner you outline.