In educational studies, furthermore, the socioeconomic level of a school or district may be estimated by the percentage of the enrollment qualifying for federal lunch subsidies. (For a critique and a discussion of some recommended modifications of current methods of measuring socioecomomic status (SES), see Entwisle and Astone, 1994).
Families rated low in SES are not only less affluent and less educated than other families but also tend to live in communities in which the average family SES is low and tend to receive less adequate nutrition and health services, including prenatal and pediatric care. In other ways, too, low SES often encompasses a broad array of conditions that may be detrimental to the health, safety, and development of young children, which on their own may serve as risk factors for reading difficulties.
Teasing apart the various aspects of the environment associated with low SES is virtually impossible, and this should be borne in mind as we discuss some particular risk factors that are linked to poverty.
As far back as Galton’s (1874) studies of English scientists, SES has consistently been shown to predict cognitive and academic outcomes (Hess and Holloway, 1984; White, 1982, Pungello et al., 1996). Although reliable, the relationship between SES and reading achievement is more complex than is generally realized.
Consider, for example, how the findings of Alexander and Entwisle (1996) that low SES students progress at identical rates as middle and high SES students during the school year, but they lose ground during the summer shed light on the relationship between SES and reading achievement.
The degree of risk associated with the SES of the individual child’s family differs considerably from the degree of risk associated with the SES level of the group of students attending a particular school. The evidence for this, and its implications for the prevention of reading difficulties among such students, is reviewed here.
In an earlier section, we turned our attention to aspects of the home environment that may be responsible for the degree of risk posed to the individual child from a low SES home.
In principle, low SES could potentially carry risk for reading difficulty for an individual child and for entire groups of children. That is, low SES is an individual risk factor to the extent that among children attending the same schools, youngsters from low-income families are more likely to become poorer readers than those from high-income families. Low SES is also a group risk factor because children from low-income communities are likely to become poorer readers than children from more affluent communities.
Because the former are more likely to attend substandard schools, the correlation between SES and low achievement is probably mediated, in large part, by differences in the quality of school experiences. It is thus not very surprising that the strength of the correlation between SES and achievement is stronger when the unit of analysis is the school than when the unit of analysis is the individual child (Bryk and Raudenbush, 1992, on multilevel measures of school effects).
When the average SES of a school (or district) and the average achievement level of the students attending that school are obtained for a large sample of schools, a correlation between SES and achievement can be calculated using the school as the unit of analysis. In a meta-analytic review of the findings for 93 such samples, White (1982) found that the average size of the correlation was .68, which is substantial and dovetails with the conclusion of the section below that attending a substandard school (which is usually one whose students tend to be low in both SES and achievement) constitutes a risk factor for the entire group of children in that school.
When achievement scores and SES are measured individually for all children in a large sample, however, the strength of the association between SES and achievement is far lower. In White’s (1982) meta-analysis, for instance, the average correlation between reading achievement and SES across 174 such samples was .23. Similarly, the correlation was .22 in a sample of 1,459 9-year-old students whose scores were obtained through the National Assessment of Educational Progress (NAEP) evaluations (Walberg and Tsai, 1985). In a meta-analysis of longitudinal prediction studies, Horn and O’Donnell (1984) obtained a correlation that was only slightly higher (.31) between SES and early school achievement.
Similar SES findings were found in population-representative studies in the United States and in other English-speaking countries (e.g., Alwin and Thornton, 1984; Estrada et al., 1987; Richman et al., 1982; Rowe, 1991; Share et al., 1984; Wells, 1985). In other words, within a given school or district, or across many districts within a country, SES differences among children are relatively weak predictors of achievement. Thus, all else being equal, coming from a family of low SES (defined according to income, education, and occupation of the parents) does not by itself greatly increase a child’s risk for having difficulty in learning to read after school income level has been accounted for.
We are not saying here that SES is not an important risk marker. What we are saying is that its effects are strongest when it is used to indicate the status of a school or a community or a district, not the status of individuals. A low-status child in a generally moderate or upper-status school or community is far less at risk than that same child in a whole school or community of low-status children.