"To the extent that education produces higher income, it is a private good. Subsidizing people to get an education is like subsidizing people to dress well for job interviews and show up on time for work. I mean, we have gotten to the point where it would not shock me to have government get involved in how people dress for interviews and in reminding them to go to work on time, but those are not what are classically considered public goods that government should provide. It could be argued that learning a core curriculum that makes you a better citizen is a public good. However, I have my doubts on that one. The politically correct citizenship education strikes me as a public bad."
EconLog, Charles Murray and the Dilemmas of Education, Arnold Kling: Library of Economics and Liberty