and 1970s and the sharp increase in
economic inequality in education outcomes in more recent decades.
Indeed, Figure 1 encapsulates two
important trends in U.S. history over
the last 50 years. In the 1950s and
1960s, racial inequality was high in
virtually every domain of life—
education, health, earnings, residential segregation—whereas economic inequality
was lower than it had ever been in the
last century (Piketty & Saez, 2003). By
the early part of the 21st century, racial
inequality was much lower (although
far from eliminated) in terms of wages,
health disparities, and residential segregation. Meanwhile, economic inequality
reached historic highs (Saez, 2012).
Although both remain high, economic
inequality now exceeds racial inequality
in education outcomes.
FIGURE 1. Income Achievement Gap and Black-White Achievement Gap
in Reading for 1943–2001 Birth Cohorts
1. 50
Average Difference in Standardized Test Scores
(90/10 Income Gap or Black-White Gap)
In standard deviation units
1. 25
1.00
. 75
. 50
. 25
Income Gap
Black-White Gap
1940
.00
1950
1960 1970 1980
Cohort Birth Year
1990 2000
Finding 2: Income gaps in other
measures of education success
have grown as well.
Academic achievement, as measured by
standardized test scores, is not the only
education outcome for which disparities
between high-income and low-income
students have been growing. The
college-completion rate among children
from high-income families has grown
sharply in the last few decades, whereas
the completion rate for students from
low-income families has barely moved
(Bailey & Dynarski, 2011). Moreover,
high-income students make up an
increasing share of the enrollment at the
most selective colleges and universities
(Reardon, Baker, & Klasik, 2012)—even
when compared with low-income students with similar test scores and academic records (Bailey & Dynarski, 2011;
Belley & Lochner, 2007; Karen, 2002).
A related trend during the last 20
years is the growing social-class gap
in other important measures of adolescents’ “soft skills” and behaviors
related to civic engagement, such
as participating in extracurricular
Source: Adapted from “The Widening Socioeconomic Status Achievement Gap: New Evidence
and Possible Explanations” (p. 98) by S. F. Reardon, in R. J. Murnane & G. J. Duncan (Eds.),
Whither Opportunity? Rising Inequality, Schools, and Children’s Life Chances, 2011, New York:
Russell Sage Foundation.
activities, sports, and academic clubs;
volunteering and participating in community life; and self-reports of social
trust (Putnam, Frederick, & Snellman,
2012).
Finding 3: The income achievement
gap is already large when children
enter kindergarten, and it does not
grow significantly as they progress
through school.
One possible explanation for the widening income achievement gap is that
K–12 schools have grown more unequal
in quality over the last few decades.
If this were true, then the gap should
grow larger the longer students are in
school. But when I examined the data,
I found little evidence that this occurs.
In one study, the Early Childhood
Longitudinal Study-Kindergarten
Cohort (ECLS-K), roughly 25,000
students were tested in math and literacy skills in kindergarten in 1998
and then were reassessed as many
as six more times between 1998 and
2007, when the students were in 8th
grade (Tourangeau, Nord, Lê, Pollack,
& Atkins-Burnett, 2006). I used this
study’s data to examine how the income
achievement gap changed as this cohort
of students progressed through elementary and middle school. As Figure 2
(p. 15) shows, the gap in reading grew
very little during this period—it was
1. 15 standard deviations when the
children entered kindergarten and 1. 25
standard deviations in 8th grade. Other
longitudinal studies that assessed students multiple times during middle and
high school show the same pattern: The
achievement gap changes little during
the K–12 years.
The fact that the income achievement