Durham, N.C.

NO one seriously disputes the fact that students from disadvantaged households perform less well in school, on average, than their peers from more advantaged backgrounds. But rather than confront this fact of life head-on, our policy makers mistakenly continue to reason that, since they cannot change the backgrounds of students, they should focus on things they can control.

No Child Left Behind, President George W. Bush’s signature education law, did this by setting unrealistically high — and ultimately self-defeating — expectations for all schools. President Obama’s policies have concentrated on trying to make schools more “efficient” through means like judging teachers by their students’ test scores or encouraging competition by promoting the creation of charter schools. The proverbial story of the drunk looking for his keys under the lamppost comes to mind.

The Occupy movement has catalyzed rising anxiety over income inequality; we desperately need a similar reminder of the relationship between economic advantage and student performance.

The correlation has been abundantly documented, notably by the famous Coleman Report in 1966. New research by Sean F. Reardon of Stanford University traces the achievement gap between children from high- and low-income families over the last 50 years and finds that it now far exceeds the gap between white and black students.

Data from the National Assessment of Educational Progress show that more than 40 percent of the variation in average reading scores and 46 percent of the variation in average math scores across states is associated with variation in child poverty rates.

International research tells the same story. Results of the 2009 reading tests conducted by the Program for International Student Assessment show that, among 15-year-olds in the United States and the 13 countries whose students outperformed ours, students with lower economic and social status had far lower test scores than their more advantaged counterparts within every country. Can anyone credibly believe that the mediocre overall performance of American students on international tests is unrelated to the fact that one-fifth of American children live in poverty?

Yet federal education policy seems blind to all this. No Child Left Behind required all schools to bring all students to high levels of achievement but took no note of the challenges that disadvantaged students face. The legislation did, to be sure, specify that subgroups — defined by income, minority status and proficiency in English — must meet the same achievement standard. But it did so only to make sure that schools did not ignore their disadvantaged students — not to help them address the challenges they carry with them into the classroom.

So why do presumably well-intentioned policy makers ignore, or deny, the correlations of family background and student achievement?

Some honestly believe that schools are capable of offsetting the effects of poverty. Others want to avoid the impression that they set lower expectations for some groups of students for fear that those expectations will be self-fulfilling. In both cases, simply wanting something to be true does not make it so.

Another rationale for denial is to note that some schools, like the Knowledge Is Power Program charter schools, have managed to “beat the odds.” If some schools can succeed, the argument goes, then it is reasonable to expect all schools to. But close scrutiny of charter school performance has shown that many of the success stories have been limited to particular grades or subjects and may be attributable to substantial outside financing or extraordinarily long working hours on the part of teachers. The evidence does not support the view that the few success stories can be scaled up to address the needs of large populations of disadvantaged students.

A final rationale for denying the correlation is more nefarious. As we are now seeing, requiring all schools to meet the same high standards for all students, regardless of family background, will inevitably lead either to large numbers of failing schools or to a dramatic lowering of state standards. Both serve to discredit the public education system and lend support to arguments that the system is failing and needs fundamental change, like privatization.

Given the budget crises at the national and state levels, and the strong political power of conservative groups, a significant effort to reduce poverty or deal with the closely related issue of racial segregation is not in the political cards, at least for now.

So what can be done?

Helen F. Ladd is a professor of public policy and economics at Duke. Edward B. Fiske, a former education editor of The New York Times, is the author of the “Fiske Guide to Colleges.”