What Explains Differences in Student Achievement?

Researchers commonly associate family income with student achievement. However, a contrarian, Harvard’s Paul Peterson, argues teacher quality, school accountability, and school choice have bigger causal impacts than family income.

Peterson’s analysis challenges the Broader, Bolder Approach (BBA) to educational reform that has been advanced by a group of education scholars, teacher union leaders, and non-profit groups. The BBA recommends that proposals to enhance teacher quality, school accountability, and student choice be dropped in favor of policies that would redistribute income and provide support services to families outside the regular school day.

BBA advocates state, “Weakening the link between income and achievement is the fundamental challenge facing America’s education policy makers.” Peterson acknowledges the connection between income and student performance, but claims most of it is not causal, but due to other factors. He cites a study by Julia Isaacs and Katherine Magnuson (Brookings Institution, 2011), that examines an array of family characteristics – such as race, mother’s and father’s education, single parent or two-parent family, smoking during pregnancy – on school readiness and achievement. The Brookings study finds that the distinctive impact of family income is just 6.4 percent of a standard deviation, generally regarded as a small effect. Peterson also calls attention to earlier research by Susan Mayer, former dean of the Harris School at the University of Chicago, which also found that the direct relationship between family income and education success for children varied between negligible and small.

Peterson says, “A better case can be made that any increase in the achievement gap between high- and low-income groups is more the result of changing family structure than of inadequate medical services or preschool education.” In 1969, 85 percent of children under the age of 18 were living with two married parents; by 2010, that percentage had declined to 65 percent.  The median income level of a single-parent family is just over $27,000 (using 1992 dollars), compared to more than $61,000 for a two-parent family; and the risk of dropping out of high school increases from 11 percent to 28 percent if a white student comes from a single-parent family instead of a two-parent family.  For blacks, the increment is from 17 percent to 30 percent, and for Hispanics, the risk rises from 25 percent to 49 percent.

Peterson claims that BBA proposals such as expanded social services, preschool, and summer programs, ignore the many hours children spend at school and amount to a “potpourri of non-educational services (that) have never been shown to have more than modest effects on student achievement.” He argues that merit pay, school vouchers, and student and school accountability have been shown to have had equivalent or larger impacts. For example, school accountability initiatives have raised student performance by 8 percent of a standard deviation. Initiatives to improve teacher quality have the potential of raising student performance by 10 to 20 percent of a standard deviation.

Peterson is probably cherry-picking studies whose findings align with his conservative political ideology. Those of us on the left do that to our detriment at times. For lack of a shorter, catchier term, call it “selective perception for findings that affirm our preconceived beliefs.”

Except for his emphasis on teacher quality, I’m not buying what Peterson is selling. Among other research challenges, it’s next to impossible to isolate the variables he values most—merit pay, school vouchers, and student and school accountability. It’s possible that the BBA-ers’ analysis, which I’m more sympathetic to, is similarly compromised by political ideology. This isn’t a sexy debate, but it’s a very important one because public resources are increasingly scarce and the outcome impacts all of us directly or indirectly.

Most likely, this is a case of the truth being somewhere in the middle—just like it’s “nature and nurture” not “nature versus nuture,” inside and outside-of-school factors combine to explain significant differences in student achievement.