This article measures the achievement impacts of 41 Knowledge Is Power Program (KIPP) charter middle schools nationwide and found consistently positive and statistically significant test-score effects in reading, math, science, and social studies.

This article draws on data and experiences observing and analyzing school lotteries from the National Evaluation of Charter School Impacts to describe challenges associated with lottery-based research. It presents evidence on the prevalence of oversubscribed charter middle schools and compares...