What is the biggest under-appreciated factor in education, and where do you learn it?
Biggest factor: Constructivism. People build their own mental models of a system based on action, and home-grown context. Talk doesn't help much. Education theory seems to understand this. Education practice? not so much.
Best way to learn it? Take martial arts for a couple years, and watch how much the Sensei DOESN'T explain...but rather makes you practice until you have an internal representation of the system...then adds 3 words to clarify your mistakes.