I have a similar opinion to yours about performance based pay. Also, I think that while it's very easy to tell a very good teacher from a very bad teacher, all the teachers in the middle of that would be pretty difficult to tell apart unless you were actually in the class.
Another problem people seem to have is that the ATARs required to get into teaching is really quite low and think that we should be encouraging the highest scoring graduates to go into teaching. I also agree with this to some extent, and I think it would help us put more value on teaching if salaries were higher and getting into it were more competitive. But at the same time, smart people don't necessarily make very good school teachers. I remember having a teacher who was very smart and extremely helpful and knowledgable if the students wanted to learn. Unfortunately, he wasn't very good at actually controlling a class. That said, I think the best teachers are both smart and can control a class.