Though some vigorously argue otherwise, the last 30 years were not a miserly time for public schools. From 1970 until now, spending for public schools increased, in today's dollars, from $3,500 a year per pupil to more than $8,000. We spend more on our public schools than the entire gross domestic product of all but 25 nations worldwide.

Among other things, these increases led to better education for disabled students, higher teacher salaries and new technologies in classrooms. Unfortunately, this influx of resources also fed a belief that the public well is bottomless when it comes to education spending. Not only is this assumption wrong, it hampers efforts to improve public schools.

Education matters more than ever to individual opportunity and America's place in the global economy, but the performance of American public schools remains wildly uneven. Many schools do an outstanding job, but overall, poor and minority students are not well served.

On average, minority students trail white students by four grade levels in achievement by the time they finish high school, and the on-time high school graduation rate for minority students hovers near 50 percent. Socioeconomic disparities are also stunning. While 60 percent of affluent students achieve a bachelor's degree by age 26, only 7 percent of low-income students do.

Education special interest groups say addressing these problems hinges almost exclusively on more money. But even if money alone would solve the problems, America does not have the luxury of spending our way to better schools. Instead, three factors - demographic changes, policy decisions and political shifts - make leaner times and hard choices more likely than continuing the fiscal trajectory of the past three decades.

First, our country is not getting any younger. While just 13 percent of the population was over 65 in 1995, the Census Bureau estimates that almost 20 percent will be by 2030. That is not a trivial change for school funding. Most states ease property taxes for seniors, provisions that are hard to change. People also spend less as they age, further pressuring states reliant on sales taxes. And fewer people will have a direct stake in public schools, creating a tougher climate for property tax referenda and school bonds—the lifeblood of local school funding.

Aging also increases pressure on state budgets. Even now, Medicaid consumes about 17 percent of state budgets, and various health care costs for an aging population will further impact states. Washington cannot help much, either. At the federal level, various entitlement programs will similarly constrain public resources for areas such as education as the population ages.

Second, more tax cuts and lower taxes are popular even as this fiscal crunch approaches. The nonpartisan Center on Budget and Policy Priorities cites state tax cuts, federal tax cuts that also impact state finances and outdated state tax policies that reduce progressivism as a primary cause of the structural deficits that many states face. Tax cuts are likewise curtailing the federal government's ability to make large investments in education.

Finally, glaring achievement gaps carry a political price. There are indications of political changes as minority parents look outside the traditional Democratic Party-teachers union coalition for political options. Meanwhile, without real improvement, our urban schools are fast becoming education providers of last resort in our cities. These issues threaten to shatter the political coalition that has supported greater funding for public schools.

While states and the federal government obviously must get their fiscal houses in order, educators must recognize and respond to the shifting demographic burden. More money is necessary to solve some problems, but the lack of funding is not all that ails our schools. Although education is more labor intensive than many other fields, schools are remarkably resilient against efforts to improve productivity and performance.

There are good ideas to stretch current dollars further. Policymakers can ensure that technology is used not only in the classroom but also to increase the efficiency of school district operations by using data to inform decision-making or through performance audits, as Gov. Mark Warner did in Virginia. A focus on attracting and rewarding quality teachers, not simply hiring more, would help improve school performance within current resource constraints. Yet there is enormous opposition to these and any other ideas that threaten to displace vested interests with a stake in the system today.

This resistance is debilitating. Debating ideas based on the policymaking environment advocates might want rather than actual conditions at hand is a time-wasting distraction from real reform. And without some reforms and improvements, there will be even less of a constituency to demand resources for public schools in a few years when the money really does become scarcer.