Most of the comments are focused on the supply of education. But I don't think the supply side is the problem, irrespective of teachers and high schools. There is more and cheaper education available than ever before. Nearly every highschooler has more access to learning that kings and emperors would have fought wars for less than 200 years ago. However,the United States, particularly in the last 50 years, seems to have fostered a culture averse to education. I believe the years long decline in test scores is a symptom of that cultural shift.