Right now, in both the US and Israel (and perhaps other countries), we're in an extreme and untenable situation, in which bad teachers cannot be fired. In the elementary school that my children attended (and that my son still attends), bad teachers were sent off to teach computers. Or science. And so forth. You can imagine what this tells the children, the parents, and the teachers about how much we value these subjects.
There was a New Yorker story a few years ago that described how bad teachers couldn't be fired... and thus were sent to a building every day, where they checked in and did literally nothing all day. Yes, they received their full salary and benefits in exchange for doing literally nothing.
I'm guessing that a reasonable alternative is to have some sort of weighted system, in which the principal's evaluation, parents' complaints, and student performance all count toward whether a teacher can be fired. The biggest thing should probably be the principal's evaluation, but perhaps if a teacher gets fired, they can get another job, in a different school -- but perhaps the parents' evaluations and the students' performance can be used to determine how many other schools they can go to before being kicked out of the system entirely.
> The last time a teacher evaluation got implemented in Pennsylvania, they dropped it in a hurry because > too many teachers couldn't pass it and they were going to have to pay WAY more to import teachers who > could.
This is perhaps the most important point: Good teachers need to be paid well. They need incentive to become teachers, and to remain teachers. Which means that people will have to pay a fair amount in order to get a good education. In the US, this will mean taxes have to go up, which is a recipe for political suicide. In Israel, this means taking money away from other things in the education ministry (since we already pay, per capita, more for schooling than most European countries).