In addition to the difficulty of rating teachers in a way that can be fairly coupled to pay, the fraction of teachers able to substantially increase their performance might be small. Identifying specific sources of confusion, inventing ways of explaining things to alleviate confusion, etc are non-trivial challenges.
What I think might be more effective than attempting to pay teachers for their teaching performance is paying teachers to produce very high-quality teaching material that other teachers can easily use themselves: detailed lesson plans, visual aids, interesting labs, textbooks, maybe even tables of sources of confusion and how to alleviate them.
What I think might be more effective than attempting to pay teachers for their teaching performance is paying teachers to produce very high-quality teaching material that other teachers can easily use themselves: detailed lesson plans, visual aids, interesting labs, textbooks, maybe even tables of sources of confusion and how to alleviate them.