571
Well, this is quite upsetting to read.
(lemmy.nz)
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.
The sixth grade thing is largely made up, but here's an article from a few years ago that references a Gallup article that references the Department of Education