Photo courtesy of Allison Shelley/The Verbatim Agency for American Education: Images of Teachers and Students in Action

Over the past 15 years, governments in the U.S. and U.K. have put quite a lot of money (by education standards) into rigorous research on promising programs in PK-12 instruction. Rigorous research usually means studies in which schools, teachers, or students are assigned at random to experimental or control conditions and then pre- and posttested on valid measures independent of the developers. In the U.S., the Institute for Education Sciences (IES) and Investing in Innovation (i3), now called Education Innovation Research (EIR), have led this strategy, and in the U.K., it’s the Education Endowment Foundation (EEF). Enough research has now been done to enable us to begin to see important patterns in the findings.

One finding that is causing some distress is that the numbers of studies showing significant positive effects is modest…