Many countries, American jurisdictions and charter schools have recently embraced longer school days or more time devoted to core academic classes. Recent research generally supports the notion that additional time raises achievement, though difficulties isolating an exogenous source of...

In a widely cited study, Chetty, Friedman, and Rockoff (2014a; hereafter CFR) evaluate the degree of bias in teacher value-added estimates using a novel "teacher switching" research design with data from New York City. They conclude that there is little to no bias in their estimates. Using the same...

A growing number of states are using annual school-level test scores as part of their school accountability systems. We highlight an under-appreciated weakness of that approach the imprecision of school-level test score means -- and propose a method for better discerning signal from noise in...

This paper investigates the effects of California's class size reduction program on teacher quality and student achievement in an effort to gain a comprehensive understanding of the impact of a large-scale decrease in class size. It uses year-to-year differences in class size generated by...

Considerable controversy surrounds the impact of schools and teachers on the achievement of students. This paper disentangles the separate factors influencing achievement with special attention given to the role of teacher differences and other aspects of schools. Unique matched panel data from...