If Knight's correct, I'd imagine it's due to a great extent because of the christian fundamentalist influence in trying to shield children from exposure to what Frank calls "evil-lusion" and what everybody else calls biology, from what Frank calls "evil-lusion" and what everybody else calls geology or earth science, from what Frank calls "evil-lusion" and what everybody else calls astronomy ... and in general from anything else that might show the Bible to be what it is.
Which explains why fundamentalism is so closely associated with low educational levels.
The alternative for those who are truly concerned about the quality of public schools and their justifiably pilloried environment is private schooling, where the exclusivity allows for a better learning environment and the teachers are still required to show a better than average intelligence.
