Overall, lower-income children are in poorer health. They have poorer vision, partly because of prenatal conditions and partly because, even as toddlers, they watch too much television, so their eyes are poorly trained. Trying to read, their eyes may wander or have difficulty tracking print or focusing. A good part of the over-identification of learning disabilities for lower-class children may well be attributable to undiagnosed vision problems that could be easily treated by optometrists and for which special education placement then should be unnecessary.
Lower-class children have poorer oral hygiene, more lead poisoning, more asthma, poorer nutrition, less-adequate pediatric care, more exposure to smoke, and a host of other health problems. Because of less-adequate dental care, for example, they are more likely to have toothaches and resulting discomfort that affects concentration.
Because low-income children live in communities where landlords use high-sulfur home heating oil and where diesel trucks frequently pass en route to industrial and commercial sites, they are more likely to suffer from asthma, leading to more absences from school and, when they do attend, drowsiness from lying awake at night, wheezing. Recent surveys in Chicago and in New York City's Harlem community found one of every four children suffering from asthma, a rate six times as great as that for all children.
In addition, there are fewer primary-care physicians in low-income communities, where the physician-to-population ratio is less than a third the rate in middle-class communities. For that reason, disadvantaged children—even those with health insurance—are more likely to miss school for relatively minor problems, such as common ear infections, for which middle-class children are treated promptly.
Each of these well-documented social class differences in health is likely to have a palpable effect on academic achievement; combined, their influence is probably huge.