It is not, as many conservatives critics suggest, due to a mysterious evaporation of the canonical texts. It was a staple of American economic life, from the founding until quite recently, that each generation would be better off than the previous one. The level of education each generation could achieve was a reflection of the growing prosperity that capitalism made possible. The education myth took hold as the Great Depression hit, as parents aspired to put their children through college as a way out of lower-class living standards. On the face of it, this was an absurd assumption.
Education is among the most economically costly activities a person can undertake.
The student leaves the workforce during what would otherwise be some of his most productive years. He graduates with ratified knowledge which may or may not help him. Only some can benefit. That's why, from ancient Greece until this century, higher education was reserved for the wealthiest and smartest segments of the population. Capitalism made the wealthy segment much larger, but it did not erase and could not erase distinctions between social and intellectual classes.