I agree that other factors would prevent students having too much power, but "good" is a very subjective term. Even "effective" depends on how the students learn. Just because I think a teacher is good for challenging me, another student might hate them for being so tough.

Even if students are colluding to give poor ratings to teachers they dislike, it won't significantly alter the relative rankings of the teachers - the better the teacher, the fewer students that are willing to systematically exaggerate the teacher's weaknesses, and the best teachers (the ones who make learning fun) won't have their scores hurt at all. Students colluding will make it hard to set a threshold for "good enough" to not fire, but even if the students catch on, it should still be a good tool for identifying the best teachers.

I mean at the end of the day it's not really an opinion question; either the survey is empirically validated or its not. At least for now it appears to be, whether it will remain so when widely used is anyone's guess. (But not up for debate, since again it's something that can be tested empirically.)

My english teacher in high school was an older, fairly harsh and not too charming lady. She was mostly disliked by my classmates. At one point they even organized a petition to replace her with someone else. I didn't sign it. In my perception, she wasn't unfair, just demanding and quite strict when it comes to grammar.

Later, whenever I met a new teacher (at university, in the workplace) lessons always seemed easy to me. I had to work hard for a good grade at high school, and her tests demanded precision and attention to detail. I started to appreciate her more.

Students are likely to prefer teachers with a pleasant attitude and lower difficulty level. A teacher easy to distract with an off-topic conversation. But at the end of the day, a teacher's job is to teach. Sure, a great teacher would combine that with charisma, ability to inspire and natural charm, but nobody's perfect.

Excellent -- then as part of a balanced review process her students' test scores would be excellent, and the principal evaluating her would have the same perspective as you.

Win!

I think you don't realize how politicized teaching has become. It doesn't matter if her students have good test scores: they all hate her. That one black mark is plenty for a determined administrator to get her fired. That a balanced review process would show see is a good teacher is simply immaterial. At least, that is how teachers see things.

Part of the reason you see so much backlash from teacher's unions against these initiatives (despite the fact that virtually all teachers acknowledge that some are better than others, and have a pretty fair idea who the worst ones are) is that they don't see this as a way to fairly evaluate teachers and improve the quality of education. Rather, they see it as a weapon to be wielded by school districts, school administrators, and angry parents ("Mrs. X told little Johnny (age: 17) where babies come from!" "Mr. Y is a member of $MARGINALIZED_SUBGROUP!" "Ms. Z believes something that is the current scientific consensus" "Mr. Q gave my son an A-") against unpopular teachers. It is an unfortunate fact of life, and even more unfortunate that so few are willing to admit it (especially here on HN, where the quality of discussion is usually above average).

We would probably have much greater buy-in from teaching unions if these evaluations were perceived as something other than politics as usual. Unfortunately, the proposals all seem to keep a some level of human involvement in the firing process (so only the very most outstanding teachers are immune to the usual political pressures). It's useful at this point to recall a bit of history: Teachers today are so hard to fire because they have tenure. Teaching unions successfully forced tenure the tenure system on school districts because school administrators of the past abused their authority to fire good teachers who happened to be politically unpopular.