Merit based Pay is hard with teachers...and probably should not be in fact the goal.
But, to allow teachers that have a TRACK RECORD of poor student scores, parent evaluations, and here is another one...other teacher evaluating. Should not get the same raises as the teachers doing better...or probably should be fired.
I believe personally, in raising teachers salaries to pull in the best talent possible, and then stop this PC crap and help the teachers design their own teaching plans (that obviously must be reviewed) and give them the power to actually discipline and remove trouble students.
So, really I believe Schools need to be pulled away from Federal Control, and away from State Control and be privately run. The States as a whole for fund them, and the Federal Government just loosely monitor all the states and insure they are teaching required basics. Then if a public school is failing because of mismanagement, then the private company can be booted out. Hell, it would take awhile to work out the plan, but it would better.
Or, if that is too complicated for you...then lets just get a good Voucher program going and allow parents to send their kids to private schools, if they choose. More private schools will open up and competition is always a good thing.