Larger Classes with Effective Teachers Lead to Significant Gains in Student Achievement

Thomas B. Fordham Institute has released a new study, Right-sizing the Classroom: Making the Most of Great Teachers, that concludes that schools can achieve significant student-achievement gains if they place more students in the classrooms of highly effective teachers and fewer students in classrooms of less effective teachers.

In the eighth grade, assigning up to twelve more students than average to effective teachers can produce gains equivalent to adding two-and-a-half extra weeks of school. These gains are seen for all students, not just those who moved classrooms. In the eighth grade, the study also showed that

_ Three-fourths of the potential gain from allowing up to twelve students to be assigned to the best teachers’ classes can be realized when allowing just six students to move;
_ Adding up to six more students than the school’s average produces math and science gains akin to extending the school year by nearly two weeks; and
_ The potential gains from moving students to the most effective eighth-grade teachers are comparable to the gains seen by removing the lowest 5 percent of teachers.

Results were more modest at the fifth-grade level.

Yet gaps existed in students’ access to effective teaching. Specifically, economically disadvantaged students in eighth grade are 8 percent less likely than non-disadvantaged peers to be assigned to a teacher in the top 25 percent of the performance rankings. This is primarily because the pool of available teachers in high-poverty schools remains unchanged under this strategy. Hence, this policy alone won’t remedy achievement gaps.

Right-sizing the Classroom: Making the Most of Great Teachers, examines longitudinal data in grades four through eight from North Carolina across four school years (2007–08 through 2010–11).