Strong correlations to actual outcomes. That can be career outcomes or otherwise but actual outcomes people care about. Not test scores.

We have a zillion natural experiments because there are so many schools in the world and within many of them teachers given a lot of leeway.

Does any of it make a damn bit of difference controlling for everything else? We have Waldorf schools teaching woodworking and cram schools shoving AP courses at eighth graders—-that’s a large difference, what do life outcomes show?