Funny anecdote... I dated a girl for a few years who got straight A's through high school and into college. Not the brightest, but she knew how to take notes, did all her assignments and passed the tests.
One day we were watching an Olympic basketball game and the screen said "2nd Half". She asked how many halves are in a basketball game. I condescendingly told her that if there are "halves" there are going to be 2. She got all mad saying, "I don't know - I don't watch basketball!" Another time, I asked her how many liters were in a 2-liter bottle... I could see her trying to work out the math in her head... She paused and said, "Wait, I know this..." I said, "Yeah, I hope so..." She asked, "So how many ounces are in a liter?" I answered, "I don't know, it's like 33.8 or something, but a liter is metric..." She says (and I'm not making this up), "Oh, well I don't know the metric system."
And that, my friends, is what a public education system gives you.