Just as President Obama has vowed to regain the initiative and push forward with his economic and education policy agenda, an organization called The First Five Years Fund has released a new poll asking the public about Pre‑K policy. According to the poll, Americans know what they want (More federally funded Pre‑K!), and know when they want it (NOW!).

Encouraging as this must be for supporters of a larger federal role in early education, opinion polling is not a good way to design policy—any more than it is a good way to design bridges. There is an aspect of bridge construction in which public opinion does properly figure: assessing demand. But when it comes to actually designing the structure that will carry living, breathing people across a gorge, public opinion plays little role. The reason is obvious: most people lack the time, skills, and knowledge to design bridges. They know what they ultimately want out of civil engineering projects, but they don’t know how best to achieve their goals.

It’s the same with education policy, and indeed with policy generally. Contrary to the apparent assumption of these early education advocates, it is not inherently obvious that increased federal Pre‑K spending will ensure that children get a strong start in life. As it happens, there is a great deal of evidence that past and current federal Pre‑K programs have proven expensive failures and have even, in some cases, done harm. Nor is the advocates’ currently favored policy–federally subsidized state Pre‑K programs–an obviously good idea. Some states with universal Pre‑K programs have actually seen their 4th grade test scores decline relative to the national average. There is no clear pattern of success.

Because of that fact, this is precisely not the sort of policy that should be expensively promoted at the federal level. If states wish to gamble that they can succeed where others have failed, then their residents should be the ones who put their money on the line. That approach has the merit that state politicians can be more easily held accountable than federal ones—voters have fewer issues on which to decide whom to support or oppose at the state level.

Well-meaning as the First Five Years Fund and its philanthropic backers no doubt are, their effort to design policy based on public opinion polling is badly misguided. It is little better than a schoolyard taunt that “everyone else wants to do it.” Serious people, people who actually want to achieve their stated goals and not simply win a political contest, can do better.