There are regulatory domains where government is wise to make its rules universal: everyone should drive on the right, for example, not just some people; everybody’s restaurant should be inspected by the health folks; everybody’s water should be free from contaminants; everybody should pass through the airport security-screening system. And more. There are also some government programs, services and benefits that benefit from extending them to everyone or almost everyone, at least on a voluntary basis. Military service. Swine flu vaccinations. Insurance for one’s bank account. And so forth. For the most part, however, turning public-sector programs into universal free goods, giving everyone access to them, and treating everyone alike, produces unintended and often undesirable results, while failing to solve the most urgent core problem.

Elizabeth Cascio’s thoughtful new study, “What Happened When Kindergarten Went Universal?” (published on the Ed Next website today) shows–to the dismay of zillions of educators–that while universalizing kindergarten may have seemed like a good idea at the time, it turned out to do more good for white kids (but only a little good even for them) than for black kids (for whom it seems to have had no educational benefit at all). If the policy goal were to equalize educational opportunity and/or to narrow achievement gaps, in retrospect America would have been better served by intensive kindergarten targeted on particularly needy kids. And we probably could have managed that on the same budget.

Kindergarten is now water under the bridge (though some states are still arguing over whether it should be half-day or full-day) but much the same lesson applies to one of today’s liveliest areas of education-policy debate, namely the “universal preschool” movement. After looking closely at this, writing a short book about it, and excerpting that book in Education Next, I can state with some confidence that, if boosting educational achievement is the goal, universal preschool, for all its surface appeal, isn’t a good use of money. A far more productive use of resources would be targeted, intensive preschool for a subset of kids who arrive in kindergarten far behind their peers.

Surely we don’t need to make the same policy blunder with preschool that it appears we may have made with kindergarten.