by Dr. Terry Stoops
Director of the Center for Effective Education, John Locke Foundation
As the Wake County Board of Education considers changes to their student assignment plan, a new study suggests that they should think twice about making class-based busing an integral part of it.
UNC-Chapel Hill sociology professors Douglas Lee Lauen and S. Michael Gaddis authored a provocative research article that will be published in a forthcoming issue of the American Journal of Sociology. Their sophisticated study, "Exposure to Classroom Poverty and Test Score Achievement: Contextual Effects or Selection?" addresses two important questions. Does exposure to high levels of classroom poverty produce lower student math and reading test achievement? If not, why do research studies often find a strong relationship between the two?
As the authors point out, for decades the consensus among social scientists and policymakers has been that exposure to classroom poverty is detrimental to the education of children. This is why a handful of urban school districts, such as Wake County, created student assignment plans that included a household income component. Between 2000 and 2010, Wake County policy mandated that schools enroll less than 40 percent of students eligible for a free or reduced price lunch, a commonly used proxy for household income. By limiting the concentration of low-income children, so the theory goes, schools can mitigate the effects of poverty on student achievement.
Lauen and Gaddis do not focus on Wake County in their longitudinal study. Rather, they drew upon a cohort or class of North Carolina public school students between their third-grade year in 2001 and eighth-grade year in 2006. Their initial analysis replicated the empirical (cross-sectional) approach used by researchers in the past. Using these methods, they found a strong relationship between poverty and test scores, as expected. But what concerned Lauen and Gaddis is that this approach provides very limited evidence of a causal relationship between the two.
Indeed, the relationship between poverty and performance weakened significantly after they adjusted for test score growth, student fixed effects (e.g., innate ability, early childhood experiences, and mother’s IQ), and time-varying confounders (e.g., changes to classroom poverty composition/type, family residence, choice of school, and student assignment over time). In the end, they found little evidence that exposure to classroom poverty directly lowered student achievement in reading and math.
With the existence of a causal relationship ruled out, the evidence suggests that previous studies likely suffered from a statistical glitch like selection bias. They conclude, "That exposure to classroom poverty has a strong association with test score in the cross-section, but has very small effects in models with weaker assumptions for causal inference, strongly suggests that selection bias is present in the cross-sectional estimates reported in studies based on point-in-time designs."
Lauen and Gaddis point out that this weakens the case for "socioeconomic integration" or class-based busing. They explain,
In response to increases in school racial segregation and the Supreme Court’s prohibition on the use of race in making school assignments, some advocate for integrating students based on socio-economic background (Kahlenberg 2001), which is constitutionally permissible. Kahlenberg (2001) argues that the best way to ensure the presence of high standards, highly qualified teachers, and less crowded classes is to ensure a critical mass of middle class families to advocate for these resources. Various forms of SES integration have been implemented in more than 50 districts across the U.S., including Lacrosse, WI; Wake County, NC; Cambridge, MA; and San Francisco, CA. The findings of the present study suggest that simply mixing students by social background may not have the intended effects, unless such mixing can garner increased resources and support for proven teaching practices that can increase student achievement in impoverished contexts.
As I wrote in a New York Times piece earlier this year, the case for using socioeconomic status as a factor in student assignment, particularly in Wake County, has never been strong. Lauen and Gaddis give us even more reason to be skeptical.
That’s what I am talkin’ about!
Facts and Stats
Lauen and Gaddis used a large dataset to carry out their study, including "a complete cohort of public school children in grades three through eight in the state of North Carolina from 2001 to 2006 (N of more than 500,000 student-year observations)."
I would like to invite all readers to submit announcements, as well as their personal insights, anecdotes, concerns, and observations about the state of education in North Carolina. I will publish selected submissions in future editions of the newsletter. Anonymity will be honored. For additional information or to send a submission, email Terry at [email protected].
Education Acronym of the Week
AJS — American Journal of Sociology
Quote of the Week
"This [study] suggests that simply mixing students by poverty level and not altering important institutional resources such as high quality instruction and teacher expectations may not have the intended effect of increasing achievement because achievement is not simply a function of poverty context but of student and family background."
– Douglas Lee Lauen and S. Michael Gaddis, "Exposure to Classroom Poverty and Test Score Achievement: Contextual Effects or Selection?" American Journal of Sociology [forthcoming]
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