Mayor Bill de Blasio has made no bones about his desire to create taxpayer-funded government preschool for every 4-year-old in New York City. Obama administration officials and some in Congress are also beating the drums to do the same for every 4-year-old in America.

But New Yorkers - and parents and taxpayers across the country - should be wary of Nanny State Childcare.

Proponents of government preschool often point to Oklahoma to make their case. The Sooner State began offering "free" preschool for every 4-year-old in 1998. Now proponents of universal preschool are touting the program as a "model of social policy," as New York Times columnist Nicholas D. Kristof recently put it.

But should this "model" be scaled-up nationwide by the federal government? President Obama has proposed spending $75 billion over the next decade to do just that, and Sen. Tom Harkin, D-Iowa, and Reps. George Miller, D-Calif., and Richard Hanna, R-N.Y., have introduced companion bills to make it happen.

Lawmakers, though, should examine exactly what wonders Oklahoma's "model" program hath wrought.

In 1998, the year Oklahoma's preschool program was put into place, the state's fourth graders had higher reading scores on the National Assessment of Educational Progress than they do today.

Fourth-grade reading scores are one of the earliest places we'd expect to see an impact from an early childhood intervention. Yet reading proficiency for Oklahoma fourth graders has been unchanged since the universal preschool program was put into place. Thirty percent of fourth graders were proficient in 1998; 30 percent are proficient today.

From 1992 to 1998 - the years immediately preceding state-funded preschool - Oklahoma reading scores were higher than the national average. Today, Oklahoma children score 4 points below the national average. In fact, Oklahoma ranks last in the nation on the NAEP for fourth-grade reading gains since 1992.

Meanwhile, Oklahoma taxpayers pay mightily for "free" preschool. State spending on the program tops $146 million annually. Yet this investment - which works out to $7,400 per child - has failed to improve the reading scores of poor children since 1998. That's a zero return on a 15-year investment.

Oklahoma's disappointing experience is not the only thing that should give lawmakers pause before jumping on the universal pre-K bandwagon. Washington's own long-running attempt at early childhood education, the federal Head Start program, has been ruled a failure even by the U.S. Department of Health and Human Services.

HHS evaluations show that the 48-year-old Great Society initiative has done nothing to improve the cognitive skills of participating children, their parents' parenting practices, their behavior, or their access to health care. In other words, it's been a $180 billion boondoggle.

Instead of expanding government preschool to middle- and upper-income families, policymakers should be concentrating on reforming - or ending - this colossal failure. In general, the best that can be said of Head Start and the Oklahoma program is that they didn't make things worse.

Decades of research, the federal government's largest existing preschool program, and evidence from the states should dissuade policymakers from embracing large-scale government preschool programs. The price tag should dissuade taxpayers.

In President Obama's proposal for universal pre-k education, the $75 billion federal price tag is just the down payment. The states would be on the hook for matching funds - "merely" 10 percent of the federal funding in the first year, but rising to 300 percent of federal outlays by year 10.

States will also find significant regulatory costs attached to those federal dollars. To be eligible, state preschool programs would have to meet dozens of expensive criteria, such as requiring preschool teachers to hold bachelor's degrees, paying mandatory increases in teacher compensation comparable with current K-12 teacher salary averages, and maintaining low teacher-child ratios.

The New America Foundation predicts that preschool programs meeting the proposed standards would cost about $8,000 per pupil per year. At that rate, providing preschool to just 75 percent of all 4-year-olds would cost taxpayers $24.6 billion per year.

To ensure excellence in education, preschool and childcare should remain the domain of families, community preschools, and church-based care - not distant federal regulators or expanded government programs.

 - Lindsey M. Burke is the Will Skillman Fellow in Education Policy at The Heritage Foundation, and Lisa Snell is director of education at the Reason Foundation.