The Effectiveness of Class Size Reduction
National Education Policy Center; June 2016
Key Takeaway: All else being equal, smaller class sizes will improve student outcomes, especially for low-income and minority children.
Policy Center; February 18, 2014
This policy brief
summarizes the academic literature on the impact of class size and finds that
class size is an important determinant of a variety of student outcomes,
ranging from test scores to broader life outcomes. Smaller classes are
particularly effective at raising achievement levels of low-income and minority
carefully weigh the efficacy of class-size policy against other potential uses
of funds. While lower class size has a demonstrable cost, it may prove the more
cost-effective policy overall.
Smart Class Size Policies for Lean Times
SREB Policy Brief; March 2012
The following recommendations can help policy-makers move toward smart class-size policies:
- Maintain rigorous and enforceable class-size policies in the
early grades: Policy-makers and education leaders should resist the urge
to relax small-class policies for early grades students, even when
budgets are tight.
- Monitor individual student achievement and engagement:
Policy-makers and education leaders should insist that schools,
districts, and the state monitor individual student performance and
behavior in grades where class sizes are increased, to prevent increased
student failure that could result from larger classes.
- Add teacher effectiveness to studies of class size: States
should undertake studies of the relationship of class size and teacher
effectiveness on student achievement.
How Important is Class Size? Defining Your Ideal
The Synergy of Class Size Reduction and Classroom Quality
Elizabeth Graue, Erica Rauscher and Melissa Sherfinski; Elementary School Journal; December 2009
The Non-Cognitive Returns to Class Size
Thomas Dee and Martin West; National Bureau of Economic Research; May 2008
- Class-size reductions improve some non-cognitive skills related to student engagement.
- Apparent long-term labor-market benefits of these non-cognitive skills.
- 8th grade class-size reductions appear to be particularly cost-effective when targeted in urban schools.
Do Small Classes Reduce the Achievement Gap between Low and High Achievers?
Spyros Konstantopoulos; The Elementary School Journal; 2008
- All students benefited from smaller class sizes.
The Wisdom of Class Size Reduction
Elizabeth Graue, Kelly Hatch, Kalpana Rao and Denise Oen; American Education Research Assocation Journal; September 2007
Health and Economic Benefits of Reducing the Number of Students per Classroom in US Primary Schools
Peter Muennig, MD, MPH and Steven Woolf, MD, MPH; American Journal of Public Health; September 2007
- Reducing class size in the early grades resulted in a net cost
savings to society of an estimated $168,000 per additional student who
graduated from high school by age 20.
- For low-income students, the cost savings per added graduate rose to an estimated $196,000.
- In terms of health, the life expectancy for added graduates increased by an estimated 1.7 quality-adjusted life years.
- Reducing class size compares favorably with childhood vaccinations in terms of quality of life years gained per dollar invested.
- Class-size intervention appears to be more cost-effective than most medical and public health interventions.
Teachers' and Pupils' Behavior in Large and Small Classes
Peter Blatchford, Paul Bassett and Penelope Brown; Journal of Educational Psychology; 2005
Do Minorities Experience Larger Lasting Benefits from Smaller Classes?
Barbara Nye, Spyros Konstantopoulos and Larry Hedges; Journal of Educational Research; November 2004
- Statistically significant lasting impact on racial and ethnic minority students in reading.
- Statistically significant lasting impact on female test scores in math.
Of Course Money Matters: Why the Arguments to the Contrary Never Added Up
Michael Rebell and Joseph Wardenski; The Campaign for Fiscal Equity, Inc.; January 2004
Economic Considerations and Class Size
Alan Krueger; Economic Journal; 2003
- Every $1 invested in reducing class size from 22 students to 15
students in K-3 yields about $2 in benefits in total increased earnings
for those students over their work careers.
Class Size: Counting Students Can Count
American Educational Research Association; Fall 2003
Class-Size Reduction: A Fresh Look at the Data
Phil Smith, Alex Molnar and John Zahorik; Educational Leadership; September 2003
What Research Says About Small Classes and Their Effects
Bruce J. Biddle and David C. Berliner; West Ed; 2002
". . . reducing the size of classes for students in the early grades
often requires additional funds, although sizable educational benefits
result when this step is taken. Students from all walks of life reap
long-lasting advantages, but students from educationally disadvantaged
groups benefit particularly. . . . no other educational reform has yet
been studied that would provide such striking benefits, so debates about
reducing class sizes are basically disputes about values. . . . If
Americans are truly committed to providing quality public education and a
level playing field for all children regardless of background, once
they learn about the advantages of small classes in the early grades,
they will presumably find the funds needed to reduce class size.”
The Class Size Reduction Program: Boosting Student Achievement in Schools Across the Nation. A First-Year Report
U.S. Department of Education; September 2002
Would Smaller Classes Help Close the Black-White Achievement Gap?
A. Krueger and D. Whitmore; 2002
The estimated impact of assigning students to small classes (15) in
the early grades instead of regular size classes (22) would reduce the
black-white gap in achievement test scores by 38% in K-3; by 15% in
achievement test scores in grades 4-8; and by 60% in test-taking rates
for a college entrance exam like the SAT or ACT in high school.
Reducing Class Size: A Smart Way to Improve American's Urban Schools
Reducing the pupil:teacher ratio to 24:1 resulted in an average 5.8 NAEP
percentile point gains among central city students. 21:1 resulted in
additional gains of 3.7 points, and 18:1 produced an additional 1.6
Reducing Class Size: What Do We Know?
U.S. Department of Education - March 1999
- Class size reduction in the early grades leads to higher student
achievement. Researchers are more cautious about the question of the
positive effects of class size reduction in grades 4-12.. The
significant effects of class size reduction on student achievement
appear when class size is reduced to 15-20 students, and continue to
increase as class size approaches the situation of a 1-to-1 tutorial.
- If class size is reduced from substantially more than 20
students per class to below 20 students, the related increase in student
achievement moves the average student from the 50th percentile up to
somewhere above the 60th percentile. For disadvantaged and minority
students the effects are somewhat larger.
- Students, teachers and parents all report positive effects from
the impact of class size reductions on the quality of classroom
Local Success Stories: Reducing Class Size
U.S. Department of Education - November 1999
"A growing body of research involving large-scale, carefully controlled
experiments shows that lowering class size in the early grades will
produce significant and lasting benefits for students. The early
implementation experience shows that the Class Size Reduction Program is
well on the way to helping schools throughout the country realize these
School Size and Class Size in Texas Public Schools Policy Research
Texas Education Agency Office of Policy Planning and Research - January 1999
- . . .small classes can provide conditions that enhance student
achievement and school climate. . . . fewer class distractions and
disruptions; increased participation; increased interactions; and
increased time for teachers to address individual student needs. The
improved climate created by smaller classes provides more instructional
- Achievement for students in small classes is greater than
achievement of students in regular size classes or regular size classes
- Class size reductions below 20 appear to be most beneficial for students, especially K-1.
- Higher academic achievement continued into higher grades for students who participated in small classes in elementary school.
- Small classes have proven successful in narrowing the achievement gap.
The Enduring Effects of Small Classes
Jeremy D. Finn, Susan B. Gerber, Charles M. Achilles, Jayne Boyd-Zaharias
Improvements in test scores attributable to attending small classes in
K-3 remained significant five years after small classes were disbanded.
Few educational interventions have demonstrated this degree of
longevity. However, in order to obtain the long-term benefits, both an
early start and continued small-class participation are important.
Smaller Classes Not Vouchers Increase Student Achievement
Alex Molnar; Keystone Research Center;1998
Why are Small Class Sizes So Effective?
The SAGE, STAR, and other studies reviewed in this report suggest small
classes promote higher achievement for a range of mutually reinforcing
- Children receive more individualized instruction.
- Teachers can focus more on direct instruction and less on classroom management.
- Students become more actively engaged in learning than peers in large classes.
- Teachers identify learning disabilities sooner, but fewer
children end up in special education classes because teachers can
support them within small classes.
- Teachers are more able to give children from low-income families and communities a critical, supportive adult influence.
- Teachers are better able to engage family members and to work with parents to further a child’s education.
- Teachers of small classes less often burn out.
The Effect of Class Size on Achievement: What the Research Says
- Students in small classes performed better than students in
large classes for both grade levels, even taking into account student
demographics, the overall resource levels, and cost of living.
- Gains were larger for fourth graders than for eighth graders. Fourth graders in small classes were one-third of a grade level
- The gains were larger for inner-city students than for any other
group. For fourth graders in inner cities, the difference was
three-quarters of a grade level, meaning that an inner-city student in a
small class could be expected to progress 75 percent more quickly than
he or she would have in a large class.
When Money Matters: How Educational Expenditures Improve Student Performance and How They Don’t
Harold Wenglinsky – 1997
Paying for Public Education: New Evidence on How and Why Money Matters
Harvard Journal on Legislation Ronald F. Ferguson – Summer 1991
An analysis of Texas data "Each additional student over 18 causes the
district average score to fall by between 1/10 and 1/5 of a standard
deviation in the interdistrict distribution of test scores for grades
1-7. This is among the strong effects for any variable in this study.”