GerryP#175:
The best book on the subject of American cultural decline since 1950s is Francis Fukuyama “The Great Disruption: Human Nature and the Reconstruction of Social Order”. Not much about the history, but sociology and moral statistics, with lots of factual material, thoughtfully analysed. And yes, these data confirm your point that decline in all aspects of culture, including education, begins with disruption of two-parent family. Statistics is very convincing.