Maximilian Bach, Birth Cohort Size Variation and the Estimation of Class Size Effects
Job talk. Maximilian Bach is a PhD researcher at the DIW Berlin and Humboldt University Berlin. He will present a paper entitled "Birth Cohort Size Variation and the Estimation of Class Size Effects".
Photo: Maximilian Bach.
We present evidence that the practice of letting poorly performing students repeat a grade affects estimates of the impact of class size on student outcomes based on withinschool variation of cohort size over time. This type of variation is commonly used to identify class size effects. First, we build a theoretical model in which cohort size is subject to random shocks and students whose performance falls below a threshold are retained. The model shows that initial birth cohort size is mechanically related to the grade-level share of previously retained students once these cohorts reach higher grades. This compositional effect gives rise to an upward bias in class size effects exploiting within-school variation in birth cohort size. Second, using administrative data on school enrollment and standardized test scores for the full student population of third graders in one federal state of Germany, we find support for this compositional effect. Correcting for the resulting bias, we find larger classes to decrease language and math test scores, and to increase grade repetition rates.
Host: Edwin Leuven