When a researcher tests an educational program, product, or policy in a randomized controlled trial and detects a significant effect on an outcome, the intervention is usually classified as something that "works." When expected effects are not found, there is seldom an orderly and transparent analysis of plausible reasons why.…

In the past few decades, we have seen a rapid proliferation in the use of quasi-experimental research designs in education research. This trend, stemming in part from the "credibility revolution" in the social sciences, particularly economics, is notable along with the increasing use of randomized controlled trials in the strive toward…