Today, Rothstein and Ali look for causes of the achievement gap. Previously, they debated whether it's worth trying to close the gap and assessed the value of the No Child Left Behind Act. Later in the week, they'll discuss reforms to boost students' performance and more.

A symptom of other inequalities

Disadvantaged students' low performance has many mutually reinforcing causes. We're the most unequal society in the industrialized world; it would be silly to expect academic performance to be equal when nothing else is. Every industrialized society has achievement gaps. Ours are bigger because our economic system is more unequal.

Educational debates are corrupted by insistence that schools alone can close achievement gaps. Certainly, better schools would lift achievement. Groups trying to improve schools, train better teachers and principals, improve curriculum and raise standards are essential. But, Russlynn, when you assert that such improvements alone can close achievement gaps, you harm the very cause of equality you hope to advance.

Closing gaps requires combining better schools with greater social and economic equality.

On Monday, I gave one example of why better schools alone can't do it, describing how low-income children have more frequent asthma, resulting in more school absence. Imagine two groups of children, identical except that one has high absenteeism from untreated asthma. When children in this group do come to school, they are often drowsy from being awake at night. Without proper medical care, they can't suppress symptoms with inhalants, as more fortunate children do. The second group has adequate medical care and less absenteeism. If both groups have great teachers, curriculum and standards, they will still differ in average learning.

Of course, good teachers will get higher average achievement from children who are frequently absent than will inadequate teachers. But will good teachers get the same average achievement from the frequently absent that they get from healthier students? Certainly not.

Because of normal human variation, some students with great absenteeism do have higher achievement than typical healthy children. And some healthy children have lower achievement than typical children with great absenteeism. But on average, the two groups must have an achievement gap.

Add to asthma the many other health differences between disadvantaged and middle-class children. Low-income children have more lead poisoning (they live in poorly maintained homes with peeling paint) and iron deficiency anemia; both of those lower IQ. The U.S. surgeon general reports that one-third of low-income children have untreated dental cavities; they're more likely to be distracted in class by toothaches. Low-income children have twice the rate of vision difficulties as middle-class children. You can't read well if you can't see well. All contribute to achievement gaps. (Readers wanting references to research that documents these claims should e-mail me at

It's not only health differences. Consider the intellectual environments of children whose parents are well educated and those whose parents are not. Children in the first group listen to complex language with larger vocabularies and are read to more often. They then attend school more ready to learn. Students from less literate homes will learn more from better teachers than from worse teachers. But will they achieve, on average, as much as children from more literate homes? Of course not. To believe otherwise is to think that learning during non-school hours has no effect whatsoever.

Consider other economic factors such as housing. Because urban rents have risen more rapidly than wages of working parents, low-income families move more than middle-class families. Some Los Angeles schools serving disadvantaged children have 100% mobility (twice as many children pass through the school annually as the school's capacity). These schools are frequently disrupted by reorganizing classes; teachers have less time to learn students' individual strengths and weaknesses. Teachers must repeat lessons for newcomers who've missed school while their home lives were disrupted. Of course, good teachers can get higher achievement from transient students than inadequate teachers could. But can good teachers get the same average achievement from transient as from stable students? Of course not.

Statistical analyses attribute about 15% of the black-white achievement gap to differences in residential mobility and 25% to differences to a few health factors. Other socioeconomic inequalities and differences in school quality also contribute.

Russlynn, you acknowledge differences in educationally important socioeconomic conditions. But you would have us keep them secret, hiding them from teachers. On Monday, you wrote that "there is great danger in sending messages to education stakeholders that the achievement gap cannot be closed. Teachers and administrators will hear leaders decry the sheer impossibility of closing gaps and ask why they should even try to teach poor and minority kids to high levels." This underestimates teachers' intelligence and dedication. Teachers do not conclude that if they alone can't fully close gaps, they must be on a "fool's errand," as you claimed. Good teachers try mightily to spur poor and minority children's learning, and they succeed more than inadequate teachers do. But good teachers also understand that instruction, to succeed further, needs greater support from social and economic policy.

Some school reformers fear that any mention of socioeconomic influences on learning will be used as "excuses" for poor teaching. But we can't avoid excuses by promoting simplistic myths about educational processes. Instead, those making excuses for poor performance should be challenged, corrected or, if necessary, removed.

The alternative — pretending that more effective schools can close achievement gaps on their own — promises the impossible, setting schools and teachers up for failure. Why shouldn't the public conclude that schools are incompetent if educators cannot achieve what some foolishly promise?

I am often accused of letting schools "off the hook" by making this argument. Not at all — both schools and social policy need improvement. But claims that schools alone can close achievement gaps let politicians and business leaders "off the hook." We let them claim one day that it's too expensive to provide health insurance to all children, and on the next pose as advocates for minorities by demanding that schools close the gap.

If schools alone could really equalize young people's opportunities, there truly would be little role for other policy to play.