Supporters of urban education frequently make the case that city schools are underfunded. Hampered by reliance on local property taxes, they contend, urban schools lack the resources they need to ensure their students succeed.

In most states, though, spending on education in rich and poor neighborhoods is relatively equal. And in states including Minnesota, New Jersey, and Ohio, city schools regularly outspend their suburban counterparts. Even in those cases, however, achievement disparities between suburban and urban schools persist. Those who advocate against increased funding for urban schools are quick to point to this fact as evidence that more money won’t make a difference.

How can this be? How can advocates allege that urban schools need more money when disparities in student achievement do not appear to be the obvious result of disparities in spending?

The idea that equal inputs will produce equal outcomes presumes a degree of similarity across families and neighborhoods. Yet generations of inequality have constrained opportunities for people in marginalized communities, often most forcefully through racially isolated neighborhoods with vastly uneven access to mainstream social, political, and economic life. Given this context, producing equal educational outcomes would seemingly require more than equal funding. It would require addressing the specific historical injustices that affect student learning—paying down what the scholar Gloria Ladson-Billings has called the “education debt.”

To fully understand the concept of the education debt, it’s worth exploring the analogy in some depth. Imagine that a person has been unjustly fired from her job, resulting in a year of lost income. To get by, she uses a credit card with a relatively high interest rate to pay her bills.

Twelve months later, after a change in management, she is brought back to her job at her previous salary—erasing any outward signs of injustice. But she has new bills to pay; by the time she is reinstated in her position, she has run up $30,000 in debt. If her interest rate is 20 percent annually, she’ll owe her credit card company $6,000 each year in interest.

How long will this person be making this $6,000 annual interest payment? Potentially forever, if she doesn’t earn enough to pay off the original balance of $30,000. Each monthly paycheck will have $500 taken out of it to cover the interest she owes, leaving her with significantly less spending power than her peers with similar salaries. Instead of spending that monthly sum on a mortgage or socking it away for retirement, she’ll be mailing it off in interest payments. Her life may have gone back to “normal,” but the consequences of her initial firing will follow her for years to come.

Black and Latino students, on average, perform below their white counterparts academically for many reasons. School curricula and norms are often shaped by white, middle-class values. Students of color are often marginalized, whether because they’re in segregated schools or racially isolated within otherwise diverse schools. Standardized testing—the primary mechanism for measuring student achievement—fails to measure particular kinds of knowledge. Perhaps most powerful, however, is the role played by historical injustice. The education debt drags on achievement in the present, and when that historical debt is combined with persistent economic and sociopolitical inequality, talk of producing equal educational outcomes with equal resources begins to sound untethered to reality.

Literacy is a useful example for thinking through the education debt. Before a student ever sets foot in school, he or she is learning from parents and caretakers—absorbing language, identifying letters, developing phonemic awareness, and building habits around reading. Literacy, of course, isn’t a heritable trait, the way that eye color is. But, because so much about learning depends on the adults in a child’s life, there is a great deal that gets passed down across generations. Which children are likely to be read to the most? Which children are most likely to have books in the home? Which are most likely to be encouraged to try sounding out words? As research indicates, parents are the key variable in all of these scenarios.

As a consequence, populations historically denied equal access, or any access at all, to education will carry that past forward. Thus, even if these people’s children were to receive equal educational opportunities in the present, they are less likely to reap an equal benefit.

It’s important to note that family income, regardless of race, is an important influence in this process. Middle-class households, for instance, are more likely than poor ones to have cars to drive to the library, money to buy books, and time to spend reading to children. But research shows that parental practices are more influential than material resources in a child’s development. And, because such practices are passed across generations, any systematic harm done to a community’s ability to support children will ripple across time; in the United States, such systematic harm has been waged on people of color.

The impact of the education debt is clear not only at the beginning of the K-12 pipeline, but also at the end of it. One of the very best predictors of whether a high-school graduate will pursue higher education is whether that student’s parents have college degrees. Even with relatively equal schooling experiences, some students will be more inclined to matriculate than others. A young person who grows up hearing about her parents’ college experiences, for instance, or being asked to think about where she will someday enroll, is likely to perceive college as a natural and non-negotiable part of the educational experience. Eighty percent of young people raised by parents with college diplomas report being encouraged to attend a four-year college—an experience mirrored by only 29 percent of students raised by parents without them. The student’s exposure to this norm and the desire to live up to expectations—to say nothing of the concrete support she might receive in the college-admissions process—helps steer her to postsecondary success.

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Failure to distinguish between equal resources and equal opportunity has significant consequences. Today, schools with lower achievement scores are routinely identified by policymakers and the public as failing; all the worse if they have resources on par with higher-performing schools. These schools, which might be generally effective, become a self-fulfilling prophecy. Perceiving achievement scores as an indicator of ineffectiveness, parents with means or know-how might actively avoid the school, thereby exacerbating segregation.

The presumption that equal resources would generate equal opportunity has also perpetuated the myth that money doesn’t matter in education. A 2011 report from the conservative Heritage Foundation concluded that “since unequal funding for minority students is largely a myth, it cannot be a valid explanation for racial and ethnic differences in school achievement, and there is little evidence that increasing public spending will close the gaps.” A large body of research, however, demonstrates that school funding has a significant impact on student achievement. And recent studies suggest that the magnitude of the impact may be greater than previously understood. While enhanced school funding, alone, might not close the achievement gap, it would almost certainly do more than an equal distribution of resources would.

Some states have crafted school-finance policies that reflect this reality. New Jersey, for instance, uses a school-funding formula that targets money significantly on the basis of student needs, as does Massachusetts. Other states have explored weighted student-funding formulas that attach different dollar amounts to students, depending on understood need. Many states do maintain flat funding formulas—or even regressive approaches to school finance—but there seems to be increasing acceptance of the fact that producing equal outcomes requires more resources for some kids than for others.

These efforts to pay off education debts might not address issues like systemic racism and structural inequality, but they could do a great deal to open up the opportunities currently reserved largely for white and upper-income children.

Many cities, for instance, currently offer support through “promise neighborhood” programs that offer a community-wide network of social, economic, and educational support services for families and young people. Cities such as New York have made investments in universal preschool, which can foster early academic skills, and over the past five years states have increased pre-k funding by nearly 50 percent. Many schools offer disadvantaged kids lower student-teacher ratios, intensive tutoring, and language support that can allow them to realize their innate gifts. And cities including Denver are spending more to recruit and retain teachers with the ability to connect with these marginalized children, empower them as learners, and draw out their potential.

All of this costs more and requires more effort than is presently being invested in the public-education system. “It all adds up,” says Bruce Baker of Rutgers University, an expert in school finance, “but it’s necessary where the goal is to provide all children with equal opportunity to achieve.”