We consider estimating the effect of a treatment on a given outcome measured on subjects tested both before and after treatment assignment in observational studies. A vast literature compares the competing approaches of modelling the post-test score conditionally on the pre-test score versus modelling the difference, namely, the gain score. Our…

Teacher professional development has long been of interest since it may affect teachers' learning, the practice of teaching, and student learning. Although empirical research has mainly explored the effect of specific professional development interventions on student achievement, these inventions have been initiated outside the school, and little…