advocated by groups like the MEA, class-size reductions are aimed at improving
teacher effectiveness by allowing teachers to focus on a smaller number of
students. Teachers would have fewer papers to grade, behavior problems to
manage, questions to answer and parents to consult; as a result,
individual students would get more attention, learn more and improve their
In a September
2007 letter to The New York Times, the NEA’s Reg Weaver clarified the union’s
position on student-teacher ratios when he stated that the federal government
needs to “provide resources for programs that improve test scores, such as
smaller class sizes. …”
In support of a federal class-size reduction program, President Bill Clinton
said: “Reducing class size is one of the most important investments we can make
in our children's future. Recent research confirms what parents have always
known — children learn better in small classes with good teachers, and kids who
start out in smaller classes do better right through their high school
Lowering class sizes does have intuitive
appeal as a solution for low-performing schools. In a meticulous paper on
class-size policies, Douglas Harris of the University of Wisconsin reported on
survey results indicating that parents and the general public overwhelmingly
support the idea of class-size reductions.
Harris explained that extensive class-size reductions passed as a referendum in
Florida even in the face of resistance from the state’s governor and of the
general understanding that higher taxes would be needed to pay for the reform.
He suggests that “one explanation for the popularity of small classes is that
parents cannot easily observe many forms of educational quality.”
Thus, he theorizes that parents may support class-size reduction policies
because they are tangible reforms that can be enacted quickly.
Unfortunately, as Harris notes, class-size
reduction may not be all that meets the eye. In a recent study of Texas student
performance, Rivkin, Hanushek and Kain found that fourth- and fifth-grade
students in smaller classes performed better in both math and reading. The
effects of smaller classes got smaller each year, however, and were not apparent in grade seven.
Nonetheless, these researchers do not advocate class-size reductions as a policy solution to low student performance. Instead, they focus on improving teacher quality. They explain that improving teacher quality by one standard deviation — i.e. getting a teacher who ranks in quality at the 85th percentile
rather than at the 50th percentile — “is equivalent to a class size
reduction of approximately ten students in 4th grade and thirteen or
more students in 5th grade, and an implausibly large number in 6th
A randomized experiment of lowering class
sizes during the 1980s in Tennessee — the famous Tennessee STAR project — also
showed that lowering class sizes in early elementary grades raised student
In this study, students were randomly assigned to three types of classrooms. The
classroom ratios were 13-17 students to one teacher, 22-25 students to one
teacher, and 22-25 students to one teacher and a teacher’s aide. Aside from
potential shortcomings in the study itself,[*]
several unintended consequences prevent this strategy from becoming a feasible
solution in Michigan. As Rivkin,
Hanushek and Kain note, the costs associated with class-size reductions do not
simply result from the costs of hiring additional teachers. The need for extra classroom space and for more support staff cannot be ignored.
Perhaps the largest barrier to this reform is
that the supply of high-quality teachers is limited, so the prospective gains
from smaller student-to-teacher ratios would likely be undermined by staffing
those classrooms with less effective teachers.
As Jay Greene writes in his book “Education Myths,” “Even if class size
reduction does produce improved performance under optimal conditions of a small,
controlled experiment like the STAR project, labor pool problems may prevent
this success from being reproduced on a large scale.”
In other words, under class-size reduction policies, schools would be forced to
hire more teachers, and those applicants may be the inferior teachers who were
passed over in prior years.
In fact, this harmful substitution occurred
during the late 1990s when California attempted widespread class-size reductions
based partly on the perceived success of the Tennessee STAR experiment.
California lowered the average number of students in a class from 28 to 20 in a
program involving more than 1.8 million students, in contrast to the roughly
11,000 in Tennessee. The price tag was over $1.5 billion per year.
Although some third-grade students showed slight achievement gains, other
reforms undertaken simultaneously in California at that time make it difficult
to attribute these minimal gains to the class-size reduction policy. Moreover,
even if class-size were responsible, the performance gains were meager given the
The California program’s evaluators were
analysts from RAND Corp. and other leading research firms. Their report
confirmed that principals had hired teachers of lower quality when the project
The evaluators found: “While [the project] was being implemented, the
qualifications of California’s teacher work force declined. The proportion of
teachers with full credentials decreased in all grades, … as did the proportion
of teachers with the minimum level of college education (only a bachelor’s
degree) and the proportion of experienced teachers (those with more than three
years of experience).”
Even though these metrics for judging teacher quality are questionable, it is
still safe to say that the quality of California’s teaching work force declined.
The California program evaluators also
reported that the class-size reduction project did not close the achievement gap
between white and minority students and that schools serving disadvantaged
students were the most likely to hire teachers with less desirable credentials.
Thus, California’s class-size reduction policy was likely a failure, due at
least in part to the low quality of additional teachers.
Given that the project cost $1.5 billion dollars relative to a total state
education budget of $34.9 billion,
the modest and nonuniform gains simply did not justify the expense.
Although they were critical of California’s
program, B.J. Biddle and David Berliner of the East Lansing-based Great Lakes
Center for Education Research & Practice are supporters of class-size reduction.
Regarding California, they suggest that lowering class sizes only to 20 students
was not sufficient to realize significant gains.
They also argue that there was not enough money to support the reform, and that,
“[T]his inadequate funding imposed serious consequences on poorer school
districts, which had to abolish other needed activities to afford hiring
teachers for smaller classes.”
Yet simply increasing the budget for education
is no trivial undertaking, and working within the reality of budgetary
constraints, policymakers should consider the trade-offs involved with
class-size reduction policies. As Jay Greene notes: “Any serious reduction in
class sizes would require us to invest a very large amount of money, so we could
only produce small classes by taking resources away from other educational
priorities. … Smaller classes would almost certainly leave insufficient funds
left over for other, much more promising reform strategies. Success in reducing
class sizes would be a Pyrrhic victory — more would ultimately be lost than
The cost of this trade-off is real, no matter
what policies one prefers. The University of Wisconsin’s Douglas Harris notes,
“Resources that go to small classes and small schools cannot be used to buy
laptops for teachers, raise teacher salaries, increase professional development,
add pre-kindergarten programs, or purchase new textbooks.”[†]
Harris also provides a helpful guide for
evaluating the costs and benefits of an education policy. He describes three
ways to consider trade-offs: cost-benefit analysis, cost-effectiveness analysis
and an “optimization” approach. Cost-benefit analysis is the most
straightforward approach; it monetizes total costs and benefits and subtracts
the former from the latter to determine the viability of a policy proposal.
Cost-effectiveness analysis involves dividing incremental benefits by
incremental costs, where incremental costs and benefits are the costs and
benefits that accrue when looking at the next unit in a series. (The term
“incremental” is equivalent to the economics term “marginal.”) The higher the
ratio of incremental benefits to incremental costs, the better the solution. The
reason that cost-effectiveness analysis is helpful is because it allows us to
compare the efficiency of multiple policy proposals even when the total costs
and benefits of those proposals are of very different sizes.
The optimization approach improves upon
cost-effectiveness by considering the concept of diminishing marginal returns.
In the optimization approach, the incremental costs and benefits are not assumed
to be linear — or constant for each new unit — as they are in the
cost-effectiveness analysis. In other words, as Harris explains, the incremental
benefit of reducing a class size from 23 students to 22 students is not assumed
to be the same as reducing the class size from three students to two students,
for example. Under the optimization approach, the ratios that are calculated
will point to the most cost-effective solution for class-size reduction by
signaling the point at which reducing the class size by one more student is not
as cost effective as the prior one-student reduction.
Without any budgetary constraints, Harris
explains, the optimization approach would be the most helpful. However, since
budget constraints do exist, and since these can easily preclude achieving the
optimal solution, the cost-effectiveness approach, even though it assumes linear
costs and benefits, is preferable.
Harris reports on his earlier analysis, which
“suggests that increasing test scores by 0.05 of a standard deviation by
reducing class size would require $1,287 in additional expenditures per pupil,
much more than the apparent $163 cost per pupil of achieving the same test score
increase through an increase in teacher salaries.”
According to Harris, his own findings are consistent with earlier research that
he claims “suggest[s] that the broad-based trend toward smaller classes in
recent decades has probably resulted in lower student achievement than would
have been possible if other uses had been made of the resources available.”
Harris is careful, however, to qualify his claims. He asserts that since
incremental costs are in fact not linear, there may be situations where
class-size reductions would be warranted. For example, Harris states that moving
from an exceptionally large class may be a good idea. Still, Michigan’s
student-teacher ratios do not suggest extremely large class sizes. According to
NEA estimates, the average student-teacher ratio during the 2004-2005 school
year in Michigan was 17.8 students per teacher, compared to the national average
In 2007, the average student-teacher ratio in Michigan was down to 17.4 students
The incremental gain to be captured by reducing student-teacher
ratios by one or two students to get to the national average — i.e., moving from
approximately 17.8 to 15.8 — would probably not be cost-effective.
Harris has made a comparison of the resources
involved in increasing teacher salaries and decreasing class sizes. As we have
shown above, across-the-board salary increases are not a particularly compelling
solution. Harris’s comparison is most helpful in demonstrating that class-size
reductions, though popular, contain hidden costs. His calculations give some
indication of the magnitude of costs associated with class-size reductions and
lend support to the arguments of those who advocate looking at policy proposals
from all angles.
One parting thought on class-size reductions:
Policymakers should also recall that self-interest may be involved when teacher
unions advocate class-size reduction policies. Terry Moe suggests that teachers
unions support class-size reductions because they want more teachers, who in
turn will become fee-payers or union members.
Douglas Harris disagrees with this notion, but argues that since class-size
reduction policies are extremely popular among teachers, unions are simply
“representing the wishes of their members.”
Perhaps Harris is right, but satisfying these wishes may not improve student
achievement, even if they make teachers happier.
The point to take from
this extended discussion of class-size reductions is that once again, the
research suggests that policymakers should focus on ways to increase the number
of highly effective teachers in the schools. As Jay Greene notes, students will
do better in a larger class with a great teacher than they will do in a smaller
class with an average or below-average teacher.
[*] For a discussion of the potential shortcomings in the Tennessee STAR study, see Greene, Education Myths: What Special-Interest Groups Want You to Believe About Our Schools — and Why It Isn't So.
[†] Research does not generally suggest that the alternative programs Harris mentions have a significant impact on student achievement. Nevertheless, Harris’ point remains: Costly class-size reduction initiatives inevitably drain resources from other possible reforms.
[**] The NEA correctly notes that student-teacher ratio is not the same as average class size, but they do concede that “no state-by-state ‘actual’ class-size information exists.” See “Class Size - NEA's Efforts to Gather Accurate Class Size Data,” National Education Association, www.nea.org/classsize/datacollection.html (accessed May 17, 2008).