Evaluating teacher quality is difficult and impossible to do perfectly. Even a simple effort to evaluate quality would be vastly superior to the current state where quality isn't even a consideration.

I agree with the ensemble of evaluations approach - student tests at the start and end of year show student attainment, student and parent feedback, peer feedback, and administrator feedback. Come up with a weighted average and experiment with it. Retain average and better teachers, reward rockstars, train underperformers, and let the bottom ranks and those who don't improve with training go.