February 2, 2006
Public schools equal or better in math than
private or charter schools
By Craig Chamberlain, Education Editor, firstname.lastname@example.org
CHAMPAIGN, Ill. — Contrary to common wisdom, public
schools score higher in math than private ones, when differences
in student backgrounds are taken into account.
That was the conclusion of researchers Sarah and Christopher
Lubienski in a study last year of data from the 2000 National
Assessment of Educational Progress (NAEP).
Now they're back with similar and more-extensive results
in a follow-up study of the 2003 assessment, drawing from a much
larger national data sample of 13,577 schools and 343,000
The results, the researchers said, raise further questions
about the assumed academic benefits of private, as well as
charter, schools. The results also raise doubts about how
effectively parental choice can influence school quality.
"The presumed panacea of private-style organizational
models – the private-school advantage – is not
supported by this (NAEP's) comprehensive dataset on
mathematics achievement," the Lubienskis, education
professors at the University of Illinois at Urbana-Champaign,
wrote in a summary of their recent study.
A paper on the study was posted today (Jan. 23) on the Web
site of the National Center for the Study of Privatization in
Education (NCSPE), based at Columbia University. The study was
funded through a $100,000 grant from the Institute of Education
Sciences in the U.S. Department of Education.
"More and more states are looking at voucher programs,
or trying to organize public schools on a private-school model,
and this study brings up serious questions about that
approach," Chris Lubienski said. "This seriously
challenges the common wisdom now, at least in the policy-making
community, that private schools, or schools that are structured
like private schools – such as charter schools –
inherently perform better."
The researchers looked at achievement and survey data from
NAEP's 2003 national sample of 190,000 fourth-graders in
7,485 schools and 153,000 eighth-graders in 6,092 schools. The
schools in the sample were categorized by NAEP as public
(non-charter), charter and private, with the private schools
broken down further by Catholic, Lutheran, conservative Christian
and "other private."
NAEP is considered the only nationally representative ongoing
assessment of U.S. academic achievement, and is often referred to
as the "gold standard" of school performance data.
NAEP tests for more than just math, but the researchers chose to
analyze math achievement because, unlike literacy, it is viewed
as being less dependent on a student's home environment and
more an indication of a school's effectiveness, Sarah
As in the previous study, the researchers found what everyone
expects when looking just at test scores: Private schools did
better than regular (non-charter) publics. "Private schools
are always going to do better if you're not controlling for
demographic differences," Sarah Lubienski said.
Charter schools scored lower than regular publics in the
fourth-grade sample, when looking just at test scores, and about
even with regular publics in the eighth grade.
However, when they compared schools with similar student
populations, based on students' backgrounds – a kind
of apples-to-apples demographic comparison – the private
schools' advantage disappeared, and even reversed in most
Using a statistical analysis known as hierarchical linear
modeling, the Lubienskis found that regular public schools scored
"statistically significantly higher" than private and
charter schools at the fourth-grade level. With 10 points roughly
considered a grade-level difference in achievement, the regular
public schools were trailed by 11.9 points by conservative
Christian schools, 7.2 points by Catholic schools, 4.2 points by
Lutheran schools, 5.6 points by all other private schools, and
4.4 points by charter schools.
At the eighth-grade level, the regular public schools were
trailed by 10.6 points by conservative Christian schools and by
3.8 points by Catholic schools.
Lutheran and charter schools led regular public schools by 1.0
and 2.5 points, respectively, and all other private schools were
2.3 points below regular public schools – but all of these
three gaps were determined to be statistically insignificant by
To determine differences in students' backgrounds, the
researchers used NAEP survey data related to the students'
socioeconomic status, which included their eligibility for free
or reduced lunch and their access to learning resources in the
home, such as books and a computer. The researchers also
incorporated survey data on students' race and ethnicity;
gender; disability and limited English proficiency.
The Lubienskis thought the gaps between regular public schools
and conservative Christian schools were especially significant
for any discussion about school choice. "Assumptions that
academic quality will be driven by parental choice need to be
re-examined in view of the fact that conservative Christian
schools, the fastest growing segment of the private school
market, were also the lowest performing," they wrote in
their summary of the research.
The researchers, who are husband and wife, caution that their
conclusions are directed at policymakers rather than parents.
They are not telling parents that the local public school is
automatically better, any more than the common wisdom should tell
parents that a local private or charter school is best. "We
could imagine sending our kids to a private school if the
circumstances were right," Chris Lubienski said.
They also noted that the NAEP samples for some school types
were limited, and cautioned against seeing their research as the
last word on the subject. "We don't think this is the
definitive answer on this issue, but I do hope that it would put
the brakes on – at least in people's minds –
about this rush to privately run schools," Chris Lubienski