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.
https://nces.ed.gov/NAAL/sample_items.asp
If you want to see some of the sample questions (from 2003 or earlier), you can see exactly the kind of questions that so many people struggle with. After reading some of the sample questions and confirming the answers, it's kind of depressing how many people are able to get them wrong.
tl;dr heh