I'm curious. I would like to know what everyone here thinks the average salary of a teacher should be.
Tough question, as there is such a small real-world (non-government) market from which to derive wages. Realistically, I'd put the range in the $30,000 to $60,000 range depending on location (and keep in mind that the cost of living in somewhere like middle Tennessee is about half of that in, say, Manhattan, New York).
In a free market, it would certainly be based on performance, but that performance would be a bit harder to measure than one might think. Test scores are a good indicator that the student has or has-not learned the subject material, but test scores don't differentiate between the teacher's efforts and skills and those of the student. A great teacher can easily be hampered by bad students. Conversely, a good student can bump up the apparent abilities of a mediocre teacher.