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.