Does Class Size Matter? (Of Course it Does!)

If you’re a teacher, the following statement won’t come as a surprise: Class size matters.

However, some still need some convincing. To those who don’t spend their days in the classroom, class size may seem like an irrelevant aspect of education. One doesn’t have to dig too deep into a Google search to find clips stating that, as long as every classroom has an excellent teacher, class size should not impact day-to-day learning. With a strong teacher, a class of 32 can learn just as much as a class of 18. Really?

While I completely agree that every single classroom in the United States should have an outstanding teaching at the helm, I also believe that a teacher shouldn’t be responsible for 32 learners at a time. Thankfully, a recent study backs up my emotionally tied belief.

A recent study by Diane Whitmore Schanzenbach of Northwestern University has found that class size does, in fact, matter when it comes to educational achievement. In her study, Ms. Schanzenback states that, “[The] critics are mistaken. Class size matters. Research supports the common-sense notion that children learn more and teachers are more effective in smaller classes.

Ms. Schanzenback’s research is based primarily on the State of Tennessee’s Student Teacher Achievement Ratio (STAR) experiment. In this experiment, close to 12,000 students and 1,300 teachers across 79 of the state’s school districts were randomly assigned to either a small or regular-sized classroom setting. The randomness of the class assignments helped to ensure the focus of student achievement was based on class size and not other contributing factors such as socioeconomic status or ethnic background.

For advocates of standardized testing, the results of the STAR data speak for themselves. Students who were randomly assigned to small classrooms (13-17 students) improved an average of 5 percentile points higher than those randomly assigned to larger classrooms (22-25). Those 5 percentile points, or 0.15-0.20 standard deviations, are enormous.

However, the results of the STAR data transcend test scores. As Ms. Schanzenback notes, “Importantly, small classes have been found to have positive impacts not only on test scores during the duration of the class-size reduction experiment, but also on life outcomes in the years after the experiment ended.” An analysis of the STAR classrooms in Tennessee as well as classrooms in California, Wisconsin, Texas, and Florida highlighted that overall levels of student engagement were higher in smaller classrooms. Additionally, teachers were able to more accurately monitor their students’ day-to-day accomplishments and reteach more frequently. In other words, smaller class sizes allow for teachers to do what they do best: guide students down their unique path towards learning.

A final portion of Ms. Schanzenback’s research that I found to be personally relevant was that smaller class sizes benefit all teachers, regardless of experience. While new teachers like myself will undoubtedly benefit from smaller class sizes, expert teacher also benefit. In fact, Ms. Schanzenback’s research suggests that expert teachers may benefit more than their novice teacher counterparts. In other words, small class sizes allow already brilliant teachers to be more brilliant, and novice teachers to begin to shine as well.

Based on Ms. Schanzenback’s research, she proposes the following recommendations to teachers, principals, superintendents, parents, and educational policy makers alike:

  • Class size is an important determinant of student outcomes and one that can be directly influenced by policy. All else being equal, increasing class sizes will harm student outcomes.
  • The evidence suggests that increasing class size will harm not only children’s test scores in the short run but also their long-term human capital formation. Money saved today by increasing class sizes will be offset by more substantial social and educational costs in the future.
  • The payoff from class-size reduction is larger for low-income and minority children, while any increases in class size will likely be most harmful to these populations.
  • Policymakers should carefully weigh the efficacy of class-size-reduction policy against other potential uses of funds. While lower class size has a demonstrable cost, it may prove the more cost-effective policy overall.

Taking all of this research into consideration, I can’t help but think of the benefits for my students. While it is hard for me to imagine what room 206 would be like with 26 students as opposed to 32, I can try. The classroom environment would be a much more conducive one. There would be space for a reading corner, a beanbag, or a bench. The classroom library could expand and student’s could have more freedom when it comes to their seating arrangements. There would be more room to breath.

Although I am an emotional advocate for education, I am also willing to bend my personal views in favor of those that are backed by research. However, when it comes to class size in the classroom, my position hasn’t changed. The research supports my beliefs. Class size matters.

Some might argue that a small class size would simply make my job as a classroom teacher “easier.” I would like to offer a different perspective. Leading a classroom of 26 students as opposed to 32 would without question benefit me as a teacher. However, it would also benefit my 26 students. After all, a better Mr. Stanford means a better classroom of learners. And that is what this profession is all about. 

Citation: Schanzenbach, D.W. (2014). Does Class Size Matter? Boulder, CO: National Education Policy Center. Retrieved [3.10.14] from

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