"If our goal is to change behaviour and drive policies towards more effective solutions, what we have done so far is a complete failure. People who are running the What Works Clearing House don’t even have a theory [of how evidence would affect policy], or to the extent that they have a theory, its been proven wrong. … We’re just deluding ourselves if we think the 5 year, $15 million studies are having any impact whatsoever."
That’s Tom Kane (somewhat echoing Lant) on the Education Next podcast. His preferred alternative to the RCT+systematic review approach though has nothing to do with crawling on any design spaces. Rather it’s doing much more quick turn-around quasi-experimental research using the multitudes of outcomes data now being collected in the US for teacher and school accountability purposes. All that’s apparently really missing is data on the actual inputs - there is amazingly rich longitudinal data on student test scores, but no record which could be matched of what textbooks are being used in different schools, or what training courses different teachers are going on. Sounds pretty sensible to me.