MDRC released encouraging results today from a demonstration, funded by Robin Hood, of two aligned interventions in New York City: Making Pre-K Count, a high-quality math curriculum in preschools, and High 5s, supplemental small-group “math clubs” provided to kindergartners. Together, the programs closed more than one-quarter of the math achievement gap.

After four decades of conducting randomised trials in social policy, Judith Gueron has dozens of maxims for researchers: ‘Never say that something about the research is too complex to get into.’ ‘If someone is unreservedly enthusiastic about the study, he or she doesn’t understand it.’ It’s hard-won wisdom, emerging from more than thirty la