In her chapter on crime in The Social Benefits of Education (Behrman and Stacey, eds., 1997), Ann Dryden Witte provides an argument against private education likely to win many economists’ immediate assent:

Consider a world in which there were no public interventions aimed at socializing children.  In such a world, each family would decide how much to educate its children in the rules of the game and how much to supervise its children’s behavior.  In making these decisions, the family would consider the socializing influence of education as it affects the family itself (e.g. better-behaved or more future-oriented children).  But it would be unlikely to give sufficient consideration to the benefit to the community as a whole of having young people who obey the rules of the game.  As a result, children would probably be undersocialized.

A few years later, my friend David Balan formalized this argument.  My reaction, however, remains the same: The facts don’t fit.  As my referee report on Balan’s original article explained:

Is there any empirical evidence that graduates of private schools exhibit lower levels of morality than graduates of public schools? I would suspect the opposite, though admittedly there is a selection problem. But that selection problem itself cuts against the thesis, for it suggests that parents who send their children to private school DO want to inculcate morality. One plausible explanation is that the externalities of morality are largely infra-marginal.

Balan’s piece focused on anti-rent-seeking socialization, but the same holds for crime, teen pregnancy, work ethic, and much more: If anything, private schools place more emphasis on good conduct, not less.  You might think that public schools would at least place more emphasis on patriotism and civics, but even that’s far from clear.  How often do religious schools even mention he potential conflict between piety and nationalism, much less urge students to make their faith their primary allegiance?  As far as I can tell, most religious schools try to instill love of God and Country, not denigrate the latter passion at the expense of the former.

You could respond, “Before the 1960s, American public schools placed far more emphasis on socialization.”  This is plausible, but note: The famous relevant Supreme Court cases expelled God from public schools, but never lifted a finger against the secular religion of American Democracy.  During the heyday of public school socialization, public schools looked more like religious schools, not less.