US education is usually poorly funded and supplemented by local levies so that poor areas get worse resources and the teachers that can make poor pay work while rich areas have fancy schools and can hire anyone. The poor areas generally need more resources, not fewer, to reach parity, because there is more need for things like free food (US schools usually hold back food from poor kids), transportation, and after school programs.

On top of this, the US is socially bankrupt. Community is regularly disrupted and so even is the capitalist nuclear family. Kids are raised in abusive conditions and have high stress households with reactionary parents that often do not care for their kids when they step outsids their preferred views. Students are often tired, hungry, and stressed. So even when they have “access” and “opportunity” on paper, they can’t make use of it, logistically or emotionally. They’re told to have drive while also lacking the energy and support to make themselves a sandwich.

So most US citizens can’t read at a “high school level”.