More (not so) fun facts:
54% of American adults read below a 6th grade level.
21% read below a 5th grade level, which is considered functionally illiterate.
High immigration numbers don't fully explain it either, as first gen immigrants only make up about 1/3 of those with low literacy.
I've studied this a little before (at graduate school) and I don't think we know exactly why, mostly because it's a ton of factors and none of the different camps in academia seem to agree on one.
Your standard Lemmy user may appreciate that late stage capitalism probably is the biggest factor, since poverty and illiteracy are hand in hand. The professor I RA'd for, for instance, just did projects that gave families money and they just did better. It was really that simple, since a ton of this is in the home, even before starting preschool.
But others have argued that there's also an anti-intellectualism in our culture (even before MAGA, kids go "ew nerds") and even more say it's pedagogy. That includes theory, like whole word vs phonics (my advisor spoke of the reading wars of the 90s like he had PTSD lol) as well as practice, like memorization vs reading for reading sake.
And, of course, the government under Bush Jr. really did the opposite of research by enacting the bipartisan No Child Left Behind which fucked both poor folk with contextless "accountability practices" while pushing soulless memorization.
Sorry for a long rant, just, y'know in 2025 onwards it's easy to forget that education has been routinely fucked, usually by conservatives. I can always explain more though, just don't want to make this comment too long, lol