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Posted at 6:00 AM ET, 10/27/2010

7 Class size myths -- and the truth

By Valerie Strauss

This was written by Leonie Haimson, executive director of the nonprofit Class Size Matters, and founder of the NYC Public School Parent blog.

By Leonie Haimson

Across the country, class sizes are increasing at unprecedented rates. An estimated 58,000 teachers were laid off in September, at the same time as enrollment was increasing in much of the country. In California, two thirds of the districts have seen jumps in class size, with many early grade classes rising from 20 to 30 students, after rules first established in 1996 governing the state’s class size reduction program were loosened.

As Don Iglesias, superintendent of public schools in San Jose was quoted as saying,

"This is not a choice that anybody is making because we think increasing class size is a wonderful thing for our schools. It's a choice because there's ineptitude in terms of our elected officials in Sacramento and their unwillingness to raise taxes or cut programs accordingly."

In Texas, there are proposals to eliminate the state’s long- standing mandate to keep class sizes in grades K-4 to no more than 22 students; recommended by the Perot Commission and implemented by Gov. Mark White in 1984– a reform which has contributed to the state’s black and Hispanic students having some of the highest achievement levels in the country.

In Florida, voters are about to decide whether to amend their state’s class size constitutional amendment, originally passed in 2002, which would freeze class sizes where they were last year ------at school-wide averages of no more than 18 students in grades K-3, 22 in grades 4-9, and 25 in high school, rather than actual classroom caps.

Clearly budget pressures are weighing on school districts, but there has also been a fierce attack on the value of class size reduction. This attack is issuing from many of the wealthy foundations advocating for corporate-style reforms, and commentators who receive funding from these sources.

A recent example was a column originally written for the Hechinger Center and reprinted on this blog by Justin Snider, who teaches an introductory writing class at Columbia University. Snider claimed that class-size reduction programs in California and Florida now “look foolish” and are a “luxury ….we can no longer afford.

Interestingly, Mr. Snider failed to mention that the writing class he teaches at Columbia is capped at no more than 15 students. Harvard College recently reduced the size of its writing classes to 10 students, in recognition of how labor intensive it is to teach students how to write well – even to these Ivy League students.

Meanwhile, public school teachers working just a few blocks away from Mr. Snider’s classroom endeavor to teach writing to as many as 34 high school students per class –and with total teaching loads of 150 students or more. Many of their students are poor and/or recent immigrants, and far more in need of individualized instruction than the high-achievers enrolled at Columbia University.

So perhaps its time to review what the research really says and what experience shows about the importance of reducing class size. Here are seven myths about class size, commonly repeated as gospel by the corporate-type reformers, juxtaposed with the facts.

1. Myth: Class size is an unproven or ineffective reform.

Studies from Tennessee, Wisconsin, and states throughout the country have demonstrated that students who are assigned to smaller classes in grades K-3rd do better in every way that can be measured: they score higher on tests, receive better grades, and exhibit improved attendance.

The Institute of Education Sciences, the research arm of the U.S. Department of Education has concluded that class size reduction is one of only four, evidence-based reforms that have been proven to increase student achievement through rigorous, randomized experiments -- the "gold standard" of research. (The other three reforms are one-on-one tutoring by qualified tutors for at-risk readers in grades 1-3; life-skills training for junior high students, and instruction for early readers in phonics – and not one of the policies that the corporate reformers are pushing.

A recent re-evaluation of the STAR experiment in Tennessee revealed that students who were in smaller classes in Kindergarten had higher earnings in adulthood, as well as a greater likelihood of attending college and having a 410K retirement plan. In fact, according to this study, the only two “observable” classroom factors that led to better outcomes were being placed in a small class and having an experienced teacher.

2. Myth: There is a threshold that has to be reached before class size reduction provides benefits.

Since STAR involved comparing outcomes between students in classes of 22 to 25 students and those in classes of 13 to 17, many critics have argued that classes have to be reduced to a certain level to provide benefits.

Yet Alan Krueger of Princeton University analyzed the STAR results for the control group of students who were in the “larger” classes and found that within this range, the smaller the class, the better the outcome.

Indeed, esteemed researchers such as Peter Blatchford have found that there is no particular threshold that must be reached before students receive benefits from smaller classes, and any reduction in class size increases the probability that they will be on-task and positively engaged in learning.

3. Myth: Large scale programs such as class size reduction in California didn’t work.

Actually, every controlled study of the California class size reduction program --and there have been at least six so far—have shown significant gains from smaller classes.

Unlike the STAR studies, nearly all elementary schools in the state reduced class size at once --especially in grades K-2nd—so it was hard to find a control group with which to compare outcomes. Also, the state exam was new, making it difficult to compare achievement gains to past trends.

Yet given these limitations, the results were striking: even when analyzing the achievement of third graders who had the benefits of a smaller class for only one year, as compared to those who were in large classes, the gains were substantial, especially for disadvantaged students in inner-city schools.

In the five largest school districts other than Los Angeles, namely San Diego, San Francisco, Long Beach, Oakland and Fresno, researchers found that class size reduction raised the proportion of third graders who exceeded the national median by l0.5 % in math, and 8.4 % in reading, after controlling for all other factors. Even larger gains occurred in schools with high numbers of poor students, and in schools that had 100% black enrollment, lowering class size resulted in 14.7% more students exceeding the national median in math, and 18.4% more in reading.

Another researcher, Fatih Unlu, avoided some of the pitfalls encountered by other researchers who were stymied by the fact that the state tests were new and there were few students to use as a control group. In his paper, he instead analyzed the change in National Assessment of Educational Progress scores, and by using two different statistical methods, he found very substantial gains from smaller classes.

4. Myth: Class size reduction lowers the quality of teachers.

This urban legend is often repeated by the corporate-style reformers. Typical is the claim from
Mr. Snider, that lowering class size in California “had the unintended effect of creating a run on good teachers: the best teachers tended to flee to the suburbs, which were suddenly hiring and which offered better pay and working conditions.

Actually, though anecdotal reports at the time warned of teacher flight, what the follow-up studies from California showed is that after rising temporarily in all schools, teacher migration rates fell dramatically to much lower levels than before, and most sharply in schools with large numbers of poor students. In fact, for the first time, teacher migration rates began to converge in all schools, rich and poor.

This finding is not altogether surprising, since teachers in high-poverty schools had better working conditions and a real chance to succeed, their incentive to flee elsewhere was substantially alleviated. Indeed, other studies have confirmed that when class sizes are lowered, teacher turnover rates fall. This propensity would be expected to act synergistically to enhance teacher quality over time, as lower rates of attrition particularly in large urban districts would tend to increase the experience level and overall effectiveness of the teaching force.

5. Myth: Class size matters, but only in the early grades.

Although there has been no large scale experiment done for the middle and upper grades, as STAR did in the early grades, there are numerous studiesthat show smaller classes are correlated with achievement gains and/or lower dropout rates in the middle and upper grades as well.

One comprehensive study, done for the U.S. Department of Education, analyzed the achievement levels of students in 2,561 schools across the country. After controlling for student background, the only objective factor found to be positively correlated with student performance was smaller classes, not school size or teacher qualifications, nor any other variable that the researchers could identify. Moreover, student achievement was even more strongly linked to class size reduction in the upper grades than the lower grades.

Two recent studies that show that class size matters, even in college. One report from the University of Richmond found that increasing class size to thirty students to 45 had a negative impact on the amount of critical and analytical thinking required in business classes, on the clarity of presentations, the effectiveness of teaching methods, the instructor’s ability to keep students interested, and the timeliness of feedback, among many other key factors of educational quality.

Another study.from Italy, found significantly lower achievement and smaller wages after graduation for college students, depending on how large their introductory lecture classes were. The effects were especially substantial for lower-income and male students:

”Our baseline results suggest that increasing class size by 20 students reduces a student’s wage by approximately 6 percent. Given this estimate, it would be hard to dismiss class size reduction as an ineffective and inefficient policy.”

7. Myth: Even if class size matters, it’s just too expensive.

Many studies have shown that class size reduction is cost-effective because it results in higher wages later in life (see the above study, for example), and lower costs for health care and/or welfare dependency.

One re-analysis of the STAR data published in the American Journal of Public Health estimated that reducing class sizes may be more cost-effective than almost any other public health and medical intervention, with large savings in health care and almost two years of additional life for those students who were in smaller classes in the early grades.

Moreover, there are some ingenious school leaders throughout the country who have managed to reduce class size without spending any more money, by redeploying out-of-classroom staff. See this study, for example, by Christopher Tienken and Charles Achilles, showing how a middle school in New Jersey managed to lower student failure rates from 3 to 6 percent to only one percent by reducing class size, at little or no extra cost.

Finally, even if reducing class size is costly, the question should be, compared, to what? As Derek Bok, former president of Harvard, once said, “If you think education is expensive, try ignorance.”

If there are only a few reforms we know have substantial benefits to children, and improve their education, health, and life outcomes, why not invest in these reforms, rather than waste hundreds of millions of dollars, and in some cases billions on unproven policies with possibly damaging consequences, including the rapid expansion of charter schools, more high-stakes testing, and teacher performance pay, as promoted by the “Race to the Top” and other federal programs?

Also, class size reduction is one of very few educational interventions that have been proven to narrow the achievement gap, with students from poor and minority backgrounds experiencing twice the gains as the average student. While many of the high-achieving charter schools, such as the Icahn charter schools in the Bronx, and those highly celebrated such as Harlem Children’s Zone, cap class sizes at 18 or less, class sizes in our inner-city public schools continue to grow.

As a recent issue brief on the achievement gap from the Educational Testing Service pointed out, schools having high numbers of minority students are more likely to feature large classes of 25 students or more, with the class size gap between high-minority schools and low-minority schools larger over time. Don’t we have a moral obligation to provide equitable opportunities to all children?

So the next time somebody with power or influence tells you that class size reduction is a waste of money, ask him what the evidence-base is for the policies he favors instead. Or ask him what class sizes were in the school his own child attends.

Many of the individuals who are driving education policy in this country, including New York City Mayor Michael Bloomberg, New York City Schools Chancellor Joel Klein and Bill Gates, sent their own children to private schools where class sizes were low and yet continue to insist that resources, equitable funding, and class size don’t matter – when all the evidence points to the contrary.

As John Dewey wrote, “What the best and wisest parent wants for his own child, that must the community want for all of its children.” If education is really the civil rights issue of our era, it is about time those people making policies for our schools begin to provide for other people’s children what they provide for their own.


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By Valerie Strauss  | October 27, 2010; 6:00 AM ET
Categories:  Class size, Guest Bloggers  | Tags:  class size, class size matters, class size reduction, education department, florida class size, leonie haimson, school reform, texas class size  
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Class size is an enormous variable in the quality of education offered as this article so aptly documents.

For anyone who has ever taught, the difference between having a class of twenty students versus thirty is like night and day, especially for the students themselves. The teacher can only do so much. The more kids in the class the less individual attention they will receive from the teacher, PERIOD.

The shame; our economy is destroying the perk of lower class sizes.

Posted by: phoss1 | October 27, 2010 7:07 AM | Report abuse

Posts like this are exactly why teachers need to teach that data can be manipulated in many ways. In graduate school (for education policy), we spent a month looking at class size. The conclusion - there is no conclusive evidence that class size "matters." Yes, there are studies that says it does. There are equal numbers of studies that says it has no effect at all.

Before I get attacked - I was a classroom teacher for 5 years and still work with inner-city high school students. My average class size was 42 - with a large of 52. I taught 8th grade social studies. In a different district, I had a class of 12. Was 12 easier? Yes. Did my students have the same level of achievement when I taught 52? Yes.

It would be great to have a counter post from someone who can show all the studies disproving everything written above.

Posted by: BrentwoodGuy | October 27, 2010 8:19 AM | Report abuse

"The more kids in the class the less individual attention they will receive from the teacher, PERIOD."

One would think the "experts" could grasp this simple idea.

Posted by: peonteacher | October 27, 2010 9:12 AM | Report abuse

Great article. I hope the country stops listening to the wealthy people, and starts listening to information like this.

Posted by: jlp19 | October 27, 2010 9:16 AM | Report abuse


"My average class size was 42 - with a large of 52. I taught 8th grade social studies. In a different district, I had a class of 12. Was 12 easier? Yes. Did my students have the same level of achievement when I taught 52? Yes."

How did you achieve this, and what was the achievement measure?

Did the same percentage of kids hand in their homework with both classes, and if so, how did you make that happen?

Posted by: jlp19 | October 27, 2010 9:21 AM | Report abuse

I think it matters. Since the number of studies is equal here's one we can all do to tip the balance. My hypothetical study: I ask 100 parents if given the opportunity "Would you rather put their child in a class of 30 or a class of 20?" Computer models reveal result would likely favor the smaller class :) Let's not get lost in all this "research" and rely on it to make our decisions for us. Use our heads...

Posted by: fishncville | October 27, 2010 9:44 AM | Report abuse

Class size does affect teacher quality, unless there is a larger pool of teachers to draw from. If you have 100 prospective teachers and you need 50, you can choose from the top half; if you need 60, you need to choose some in the lower half.

Ask baby boomers how many teachers we had who were hired so rapidly they didn't even know their way around the school on the first day. I remember being put in a combined class of 10 fifth-graders and 10 sixth-graders. Supposedly, we were chosen because we could work independently; we had to, since most of us knew more than the teacher. About that time, the superintendent of education in a neighboring state was quoted in the paper as saying the almost any graduate of a college of education in his state got a job: "If they don't pass the state test here, we tell them to go to [name of our city]. They need teachers so badly they will hire anybody we send them."

If a school needs 10 teachers, that school will hire 10 teachers, regardless of their qualifications.

Posted by: sideswiththekids | October 27, 2010 10:08 AM | Report abuse

Here is another angle of looking at the picture of class size (American Journal of Public Health 2007):

Health and Economic Benefits of Reducing the Number of Students per Classroom in US Primary Schools

Posted by: shadwell1 | October 27, 2010 10:12 AM | Report abuse

At the same time our country appears willing to send every soldier in Afghanistan every gun and protective gear they need to _______(fill in the blank), we are wasting time and money on studies of the obvious.

I guess studies aren't tied to property taxes. The only classes where large size is an advantage is something like band or orchestra, when a large, booming sound or dramatic effect is desired.

Mr. BrentwoodGuy sounds like he knows how to walk on water, too. Not every teacher is a miracle worker. And most teachers from schools with large classes in the 50s and 60s hit children or sent them to the office to be paddled if they did not comply.

Meanwhile, our academic teachers are becoming increasingly mired in the desolate, data-driven swamps of paperwork, the true teaching life being choked out of them. The arts and humanities teachers are either being squeezed out or being marginalized in favor of the technological gods.

Perhaps it's time to tie the military budget to property taxes and give teachers whatever they need to meaningfully educate the next generation.

Posted by: PLMichaelsArtist-at-Large | October 27, 2010 11:14 AM | Report abuse

I wanted to say something smart about what kids deserve and justice, but John Dewey beat me to it. Again!

For those who still cling to hope that Rhee "reforms" will continue in DCPS after her departure in 3 school days - does anyone seriously still want this for kids? seriously? - there are plenty of programs and mandates that help automaton teachers will be barking at large classes. There are instructional mandates (called interventions by some) for low test-scoring schools. One of them uses nearly scripted texts for teachers, allows for scarcely any individualization, and would be perfect, just perfect! for large classes of children who, if they didn't already, will soon hate reading.

yes, for any of us who value actual student learning, class size matters. It's a heck of a lot of work devoted yourself to a kid's learning. Unless he or she is just a peg on the color-coded reading chart.

Posted by: dcparent | October 27, 2010 11:26 AM | Report abuse

To the "Brentwood guy" commentator above:

the number of studies that show that class size matters far outweigh the number of negative studies. For a count go to the Alan Krueger link above or go to

The highest quality studies have an even greater preponderance of positive findings.

Posted by: leonie1 | October 27, 2010 11:55 AM | Report abuse

I can't believe that Ms Haimson even had to take the time to write such a piece. It shouldn't be necessary to explain to an education chief the importance of smaller class sizes. Otherwise why would private school parents be willing to spend 35K for first grade just for this reason? And why would they bestow smaller class sizes on their beloved charter schools? It is beyond hypocritical to even argue the point at all.

If anyone is tempted to cry budget and that public schools are "free", I can only speak for New York and say that this city has given 30 year tax abatements (our money) to totally as of right developers to lure new families to the city, to the tune of billions of new tax dollars downtown alone, and stunningly without planning any new schools. What did they do with this money? These people came here for this reason alone and now they have either a class size of 35 or a waitlist spot to look forward to. This, while concurrently daring our public school teachers, under these impossible circumstances, to raise test scores. It's beyond reprehensible in addition to being illegal.

For the life of me I cannot understand why we have Education heads that are not educators. They are mostly lawyers, whose children went to private school. How on earth can this possibly be a productive combination?

Frankly I would like to know where our president stands on this; perhaps some good federal representation on the topic could affect real change.

Posted by: tricia7 | October 27, 2010 12:20 PM | Report abuse

When I saw the title of today’s posting (“7 Class size myths -- and the truth”] my thoughts flashed back to a similar Washington Post headline: “5 Myths About Schools That just Can’t Be Fixed” (February 22, 2009). It’s purpose: to “dispel some empty theories about how to help them.”

I had noted them at the time because they seemed to fit exactly with the work I’d been doing to challenge the seldom-questioned thinking that shapes what schools do everyday.

His myths were:
1. We know how to fix public schools; we just lack the political will to finish the job.
2. Teachers know best how to teach kids; policymakers should leave them alone.
3. The federal government meddles too much in the affairs of local schools.
4. Teacher unions are the enemy.
5. There's no place in education for politics.

Then as I began to read it, I initially found myself agreeing that these five assumptions had now become ‘beliefs” about what’s “true,” and were currently influencing the scope and nature of most major efforts to fix schools so they can work for all children all the time.

But something about them didn’t fit with my thinking. Were these beliefs actually “myths?” So I went to the dictionary and found five definitions. Two stood out:
• the 1st, "a story without a determinable basis of fact or a natural explanation;” and
•the 5th, “an unproved collective belief that is accepted uncritically and is used to justify a social institution…”

There was a distinct difference between the author’s understanding of the 5 conditions he correctly presented as influencing the national frustration with 40 years of attempts to fix schools… and what I had been learning from my work with a major urban school system engaged in fixing itself systemically.

The article’s “myths” seemed based on “unproved collective beliefs” about what’s true, right or natural, but which were not “natural explanations” for the underlying truths.

But for 12 years I had been observing and documenting the on-the-ground systemic experiences of a major school district that has been effectively challenging each of those five “collective beliefs” by the only way possible – transforming its work processes into systemic “belief”-changing experiences. And my learning was generated by using different “natural explanations” for their thinking and actions. This enabled me to ask different myth-challenging questions that better identified the core “truths” that this present posting addresses.

So what I’ve continued to learn is that we have some “myths” about “myths” …and maybe our myth-challenging search for truth and “answers” needs to dig down one level and start with some different questions.

Posted by: lewrhodes | October 27, 2010 2:14 PM | Report abuse

As usual, excellent research and compelling arguments. One of my questions has recently been: in the face of the evidence, why is it being ignored by the Powers that Be? I can only come to the conclusion that THEY KNOW WHAT THEY'RE DOING IS WRONG but the alternative would be to empower a lot more people to have the critical tools to recognize the hypocrisy and economic injustice of the current political and economic system. That is what they fear losing and will make all sorts of elaborate excuses and obfuscations to preserve.
I wouldn't suggest that this is a national conspiracy, but it is a commanality of self-interests that wants a low-educated, uncritical, consumer-addicted electorate that can, as it seems the coming election will show, be easily distracted, lied to, and manipulated.
In further support of your own findings is a recent, very entertaining video by Sir Ken Robinson that is worth seeing. He confirms that "collaborative learning" was far superior to the isolated paradigm that is more likely in a large classroom. The video loaded with interesting ideas and best practices:

Keep on keepin' on Leonie

Joel S.

Posted by: shatzkyj | October 27, 2010 3:53 PM | Report abuse


Okay, so you had some interesting points but you never really addressed the issue. You left us with "dig deeper" and "develop better questions." I'm not sure that this helps me identify your position on this issue.

Posted by: DHume1 | October 27, 2010 4:31 PM | Report abuse

DHume1 - You're right...I do have a definite position on this issue...and I couldn't fit it into the "Comments" space. It's accessible though on the website and blog I developed with the support of 2 national organizations promoting new ways to "re-think" what organizations like schools do.
I'm not sure if Answer Sheet accepts direct links, but if not, it's
If you can get to it, I'd enjoy discussing your thoughts about the deeper issues.

Posted by: lewrhodes | October 28, 2010 7:41 AM | Report abuse

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