Quasi-Experimental Estimates of the Effect of Class Size on Achievement in Norway

Using a comprehensive Norwegian administrative database, we exploit independent quasi-experimental methods to estimate the effect of class size on student achievement at the end of lower-secondary school. Identification based on maximum class-size rules and population variation (and variations on these methods) give very similar estimates. We cannot reject that the class-size effect is equal to zero, and can rule out effects as small as 1.5 percent of a standard deviation for a one-student change in class size during three consecutive years.