We have friends who got tuition reimbursement from their employer to go to the local two year college. They did this fifteen to twenty years after graduating high school. One, who's not that sharp, needed three remedial math classes until one that actually gave college credit. Another couldn't write at a seventh grade level, but was quick to improve once told what was wrong with the writing and why. Both went to suburban/exurban schools in Mid-Michigan.
Another couldn't write at a seventh grade level, but was quick to improve once told what was wrong with the writing and why. My wife teaches at the local CC. She encounters students who can't compose a single sentence without mistakes, who have never been taught any English grammar. How can they write correctly if they haven't been taught? Apparently, the only language instruction they received was, "Be creative".
As others have pointed out, sometimes the classes have older students (40s, 50s+). They are aghast at what the younger ones don't know.