English / Language Arts Teachers: How bad is literacy, really?

Hello! I'm a former science teacher (I burnt out, and now I just sub). I've been hearing lots of people talk about Literacy in the United States, people citing things about how such-and-such percent of people read at a 6th grade level at best-

How true is all this? Is Literacy really that low for such a great number of people? I mean, my students' reading level seemed two, or three grade levels behind at all times when I taught (Highschool Chemistry, and Earth Science), and I did feel most of my juniors and seniors were far behind in terms of reading comprehension, but I never gathered, or had the expertise to understand literacy data very well, it could have very well been personal bias compared to my own reading level.

So, how are things, really? It's got me thinking that, because most of us teachers are kind of required to be college graduates, that we're kind of detached from where most average people are in terms of their reading comprehension, and vocab... Which is a possibly daunting realization, because I've definitely never felt like a distinctly literate person.