Conversation

Absolutely and passionately agree: avoid "impact metrics in education" like the plague. If you don't know in your gut (or haven't been convinced by direct observation) that what you're doing works, just don't do it. Don't waste time chasing someone else's tail. Life's too short.
Much of our knowledge is never made explicit. This is true of moral knowledge, which is about what to do and what to want. The upshot is that no stated metric captures everything you care about. And of course one's fallible, too, and may need to revise one's wishes in any case.