This paper introduces a variation on the post-test only cohort control design and addresses questions concerning both the methodological credibility and the practical utility of employing this design variation in evaluations of large-scale complex professional development programmes in mathematics education. The original design and design…

Too many students in high-poverty, urban communities drop out of high school, and too few graduate prepared for college and careers. Three national organizations--Talent Development Secondary, City Year, and Communities In Schools--have formed "Diplomas Now" in an effort to transform urban secondary schools so fewer students drop out and…