You see, teachers are tasked with producing learning, and learning is an emergent property - it must be produced in context and in real time. What I learn in one context doesn't necessarily translate into another without re-learning in that context and real-time experience. This makes determining the quality of a teacher a difficult task - but one we must figure out.
The interesting thing to me is that if I walked into any local high school and stopped 15 random kids and asked them to tell me who the best and worst teachers in the building are, I'd get a pretty consistent list of names and reasons. Same applies to principals, secretaries, etc. So why is it so hard to escape the old experience and education linear progression of pay, seniority and security?
What say you?