Score contribution per author:
α: calibrated so average coauthorship-adjusted count equals average raw count
This note implements two research designs that attempt to isolate the effect of class size on achievement. A first strategy focuses on variation in class size in rural schools with fewer than 30 students, and hence only one classroom, per grade. Second, an approach similar to Angrist and Lavy's exploits regulations that allow schools with more than 30 students in a given grade to obtain an additional teacher. Both designs suggest class size negatively affects test scores. © 2006 The President and Fellows of Harvard College and the Massachusetts Institute of Technology.