Not surprising.
I went to one of the best public districts in one of the most educated states in the country. I had a class my senior year that was required, so any given class was a random mix of students from my grade.
There were at least 3 of them, in a class of 30-ish, that I would classify as functionally illiterate. They still graduated.
I frequent another forum that is in English, but has a fairly high number of people from other countries, both English-speaking and not. If I see someone who can't seem to spell simple words or use correct grammar, dollars to donuts it's an American.
I tutored in English for a while, both for general students as well a ESOL students. My American students routinely struggled more with simple mechanics, even compared to my ESOL students.
The majority of my own education was at home. In retrospect, my father seemed to be fighting a constant battle to maintain my sense of curiosity despite the onslaught of education, which is mostly built simply to make you stay in line, rather than to teach you anything.
I remember when I brought my class work to my dad one day, and he saw my SQ3R notes. It's basically how they teach you to think, without any actual thinking involved.
He put his head in his hands and said, "Good lord." He was silent for another minute before he said, "Ok. I want you to pretend this isn't a real thing. Just memorize it like a passage out of a fiction book in order to pass your quiz, and then forget it exists. Ok?"
I never realized what a depressing moment that really was until several years later.
): 
