Politicians all talk about “fiscal responsibility,” but few put that principle into action– particularly when faced with a call for a politically attractive program. Governor Mitt Romney (R., Mass.) deserves applause for doing just that by vetoing a bill last week that promised to provide universal preschool to Bay State toddlers.

Massachusetts is the latest state to consider expanding government-provided education to the juice-box set. Virginia Gov. Tim Kaine (D.) is trying to fulfill his campaign promise to give all parents the option of enrolling their children for a year of school before kindergarten. Illinois Gov. Rod Blagojevich supports subsidizing preschool for all three- and four-year-olds. Georgia and Oklahoma already offer all four-year-olds pre-K. Earlier this year, California voters considered (and rejected) a ballot initiative to provide preschool to all California four-year-olds.

Despite the proposition’s failure in California, it’s easy to see why many politicians view universal preschool as a political winner. Voters picture smiling four-year-olds clasping lunchboxes, heading off to bright colored classrooms to begin a life-time of learning. Presumably, the extra year of school will give these children a leg up, and clever budget-crunchers promise that early-learning investments will pay future dividends of higher tax payments and reduced spending on social programs. An added bonus: Over-stressed working moms have one less year to worry about finding daycare.

But universal preschool doesn’t live up to its promise, either as a matter of policy or of politics. While proponents boast of preschool as having a dramatic affect on student outcomes, there is scant evidence to support this claim. Darcy Olsen, president of the Goldwater Institute, reviewed the major studies on preschool’s effects and found no evidence that preschool helps mainstream (neither low-income or learning-disabled) children learn more. Moreover, some studies have shown that preschool– even as little as three hours a day or fifteen hours per week– can actually impede these children’s social development.

Some children, particularly disadvantaged children, have been found to enjoy some benefits from intensive, high-quality preschool. But preschool’s positive effects are short-lived. For example, a study conducted by University of California Santa Barbara researchers found that the academic gains made by children in preschool vanished by third grade.

Ineffectiveness isn’t the only strike against government-provided preschool. Voters and politicians should also consider if government should be in the business of educating children as young as two. Anyone familiar with the K-12 school system’s underwhelming results should question the logic of expanding government-run education. Each year in the public-school system, American children fall further behind their peers overseas. Fixing the existing public-school system seems like it should be a higher priority than giving them even more children to educate.

Government provision of preschool would also be another step in the creeping government takeover over what had been family’s responsibilities. As Olsen writes: “At heart is the question of in whose hands the responsibility for young children should rest. On that question, plans to entrench the state further into early education cannot be squared with a free society that cherishes the primacy of the family over the state.”

Parents agree, which is why initiatives to expand government’s role in preschool and childcare often fail. Parents are not clamoring for government-provide preschool or daycare programs. In fact, most parents believe that children are better off spending more time at home with parents than in organized daycare facilities.

Universal preschool is not the way to help parents realize that goal. These programs are expensive. Without Gov. Romney’s veto, Massachusetts taxpayers would have faced a billion-dollar-per-year price tag. Virginia’s program would cost $300 million annually. Families would see their tax burden rising, making it more difficult to make ends meet on just one salary.

Policymakers should join Governor Romney in opposing universal preschool. It may sound like a political winner, but when government expands, we all lose.