Here is a good article from the Pittsburgh Tribune on Will Fitzhugh and his efforts at waking people up to the fact that less and less serious reading (and writing) is required of American students.
Although the origins of this problem aren’t discussed, I suspect that it has a lot to do with the changing nature of teachers. The education theorists think it’s much better to have teachers who are warm, nurturing, self-esteem boosting types rather than those who care deeply about books, learning, and precise thought. As older teachers who don’t hold with “progressive” theories retire and are replaced with young ones who have been steeped in such theories in their ed school courses, it’s natural to expect that requirements for difficult reading and writing assignments would fade away.
A couple of good books on the degradation of high school are J. Martin Rochester’s Class Warfare and Sol Stern’s Breaking Free.