Is It Better to Have a Great Teacher or a Small Class?

A new report suggests that students are better off in a larger class taught by an excellent instructor.
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Mari Darr-Welch/AP Photo

When it comes to student success, “smaller is better” has been the conventional wisdom on class size, despite a less-than-persuasive body of research. But what if that concept were turned on its head, with more students per classroom – provided they’re being taught by the most effective teachers?

That’s the question a new study out today from the conservative Thomas B. Fordham Institute set out to answer, using data on teachers and students in North Carolina in grades 4 through 8 over four academic years. While the results are based on a theoretical simulation rather than actually reconfiguring classroom assignments in order to measure the academic outcomes, the findings are worth considering.

The research on class size is mixed, and modest efforts–taking one or two students out of a room with more than 20 kids, for example–haven’t been found to yield much benefit on average. The enormous expense of paring classes down to the point where research has suggested there’s a measurable benefit for some students is simply beyond the fiscal means of most districts. As a result, everyone from U.S. Secretary of Education Arne Duncan to philanthropist Bill Gates has urged districts to consider waiving class size policies in favor of giving more students a chance at being taught by a highly effective teacher.

To test the merit of that approach for Fordham, senior researcher Michael Hansen of the Center for Analysis of Longitudinal Data in Education Research (CALDER) simulated what might happen if the North Carolina teachers with stronger track records had more crowded classrooms. (The class sizes in the data set had some variation within schools, from about 21 to 24 students depending on the grade and subject.) The model factored in an estimated loss of effectiveness due to the bigger class size.  Among the school-level findings:

  • At the eighth-grade level, assigning up to 12 more students to the strongest teachers could produce learning gains that were equal to 2.5 weeks of additional instruction (gains were more modest at the fifth-grade level). 
  • Schools could see 75 percent of that gain just by moving six students, suggesting drastic class size increases aren’t necessarily required. 
  • Moving a few students to the top-performing eighth-grade teachers could produce gains equivalent to removing the bottom 5 percent of teachers. 

An important point: Students selected to move from smaller classrooms into bigger ones with more effective teachers would see the biggest gains, according to the simulation. Kids who remained in the downsized classrooms also would see a slight benefit as their weaker teacher’s performance improved with a smaller student load. 

When it comes to research, randomized studies are typically the gold standard. But conducting them in academic settings is costly and frequently requires the cooperation of many parents and school administrators. A simulation is less risky, and can potentially soften the ground for new ideas. However, it often takes a deeper look to identify and explain influences that might factor into the performance of both the students and their teachers.

Much of the research on teacher effectiveness focuses on reshaping the workforce, said Hansen. That’s why he wanted to see what could be done to improve outcomes for students assigned to teachers already on the job.

“What we’re doing here is saying, 'OK, some students are going to be lucky and get the stronger teacher, and some students are going to be unlucky and get a weaker teacher,'” Hansen told me. “By intentionally unbalancing these class sizes, we’re making a few more students lucky.” 

If there was a surprise in the new Fordham report it might be that top quartile of teachers were already teaching roughly a quarter of all the students, said Bryan Hassel, co-director of Public Impact, a Charlotte, N.C.-based organization that works with districts across the country on school improvement initiatives. That statistic meant the schools weren’t distributing students based on teacher talent, but were likely making assignments based on simple math. 

“Ideally, schools would focus on increasing the number of students their best teachers have responsibility for,” Hassel said. “I would think there would be some effort on the part of schools to push in that direction.” 

Hansen said he would like to see the the findings reach school-level administrators (typically principals) with the authority to adjust classroom assignments based on a teacher’s effectiveness.

“What I hope the study does is help them understand there are potentially large consequences to this seemingly mundane task,” Hansen said. “By putting even just one or two more kids in a more effective teacher’s class, it can make a difference. There are meaningful gains from relatively small changes.” 

While the student learning gains simulated in the study are encouraging, the achievement gap remained for economically disadvantaged students. Hasten said that’s because his simulation only moved students within a school. That doesn’t change the fact that some schools have more effective teachers than others, and the ones with the most socioeconomically challenged students are typically more likely to employ new and/or underperforming teachers. As the report concludes, “class-size-shifting strategy alone cannot reduce preexisting inequalities, and some other intervention would be necessary to remediate entirely gaps in students’ access to the best teachers.” The simulation may not solve all of the underlying issues, but it's moving the needle in the right direction, Hansen said.

Some districts are already experimenting with creative approaches to expanding the reach of their best teachers, whether it’s through using video-conferencing to record their lessons or creating new positions where they have opportunities to work with more students without adding to their class sizes. Public Impact is working with schools in Charlotte, N.C. and Nashville on this very issue, said Hassel. Charlotte created 19 positions where teachers would take on additional student responsibilities with a sizable pay bump, and the district received more than 700 applications, Hassel said. 

Sarah Almy, director of teacher quality for The Education Trust, a nonpartisan organization in Washington, D.C. that focuses on closing achievement and opportunity gaps in public schools, told me the premise of the Fordham study is worth exploring. But Almy added that the problem of the weakest teachers often being relegated to the neediest students needs to be confronted. 

Rearranging classroom assignments “is only going to go so far in terms of creating more equitable access for kids,” Almy said. “It’s not just about getting more kids within a building to highly effective teachers, but getting more highly effective teachers into the building.” 

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Emily Richmond is the public editor for the National Education Writers Association. She was the education reporter for the Las Vegas Sun from 2002 to 2010, and in 2011 she was Knight-Wallace Fellow at the University of Michigan. She blogs at www.educatedreporter.com.

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