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.
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.

Presented by

Emily Richmond is the public editor for the National Education Writers Association. She was previously the education reporter for the Las Vegas Sun.

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