Because these elite schools and colleges are also highly visible -- and where the "chattering classes" want (and can afford) to enroll their own daughters and sons -- they create a façade of private-sector vitality. Behind it, however, like the Wizard of Oz's curtain and Potemkin's building facades, there is much weakness, a weakness that probably afflicts the vast majority of today's private schools and colleges.

Is this situation reversible? And should it be a matter of concern for education reformers and policymakers?

Most other modern countries have essentially melded their private-education sectors into their systems of public financing -- and have accepted the tradeoffs that accompany such financing, namely government regulation of curriculum, teacher credentialing, student admissions and more. We can see early examples of this in the U.S., too, as vouchers gradually spread and private schools accommodate themselves to the state testing regimes and other rules that come with such financing.

This is apt to be a limited remedy, however, due to American church-state entanglement anxieties that other countries don't share; prohibitions in many state constitutions that make such public financing difficult or impossible; and our conviction that what's valuable about private education is its freedom to be different. The policy dilemma is whether different-ness is precious enough, if with it comes gradual erosion of the "different" sector itself.

One can also fairly ask whether U.S. private schools and colleges are really all that different from their public-sector counterparts. In practice, their education-delivery model is practically indistinguishable, save for the accoutrements that the wealthiest of them can buy (trips to faraway lands, nifty technology, tiny classes, etc). There is, however, a difference where religion is concerned: Just 22.8 percent of K-12 private-school students are in secular schools, while about 32 percent of all private college students are enrolled in religiously affiliated institutions. In less prosperous schools and colleges, religion may, at day's end, be the only real difference between public and private -- and the return on that investment, while perhaps significant, cannot be easily measured.

Changing the delivery system might serve to make private education both more affordable and more different, and signs of such change are already evident, but rarely in the traditional nonprofit portions of the private sector. Instead, the boldest innovations are coming from entrepreneurs, most of them profit-seeking and most of them delivering instruction (and more) via technology rather than face-to-face in brick buildings that are open just six or eight hours a day for 180 or so days a year.

Or elite universities -- the ones that are still thriving and would continue to thrive without these changes -- are, themselves, innovating -- mostly for students other than their own. The MITs and Stanfords are teaming up with the Courseras and Udacitys -- educational technology companies specializing in online education -- to offer online courses to thousands. Udacity has put a toe into the K-12 waters, both by partnering with local school systems and by inviting students to enroll directly in its college-level courses. Nor is it likely to stop there. Indeed, I expect "St. Paul's math" and "Dalton's literature" in time to echo across the land, too. If current trends continue, we're going to see a bi-modal system develop, with public schools (including charter schools) and ultra-elite private schools monopolizing the education space as the plethora of smaller private and parochial schools that once fell between them gradually fade away.

Can run-of-the-mill private schools and colleges reboot? Can they change themselves -- including both their delivery systems and their cost structures -- enough to brighten their own futures? I wouldn't bet a year's tuition on it.

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