You asked, so my appologies, but this is going to get a little preachy.
![Oops! :oops: :oops:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
Not on any one measurement alone. My first thought is test score delta from beginning of the year to the end. The principal also needs to have his/her own assessment of the teachers performance. I would also have confidential, independent peer evaluations provided to the principal. The Principal would have a raise pool and he would determine how much of that pool is given to each of his/her teachers.
My kids attended public school in an affluent community where most students had a solid family background and where education is a very high priority of the parents. Everybody goes to pre school and they show up to Kindegarten well prepared both in terms of behavior and academics. There are signup sheets for parents to get the opportunity to come in and help in school because there are too many volunteers. This school system is always among the most highly rated if not the top. The biggest challenge for teachers often is satisfying the parents.
My wife teaches Kindegarten in a school system with a very high ratio of "free and reduced lunch" students. There is a very high percentage of students with single mothers working two jobs to support multiple children. Many of her kids don't see their father much and some don't know their father. The result sadly, is kids showing up to the beginning of their school career having never been to pre school, not knowing colors, numbers, or any letters. Many of the kids have not been taught how to behave by anyone/anything except the streets. They do know how to cuss like sailors and to make themselves the center of attention in the most negative ways. Quite a few each year have emotional issues or ADD/ADHD. These kids then take tests that have content which was 1st and 2nd grader level just a few years ago.
I go in a day or two early each year just to help her get them started. I usually spend my day with one or two of the worst behavior kids to allow my wife to get the rest of the class into some level of control so she can then deal with the biggest challenges while teaching the class.
She works and fights to teach these kids and give them the basics of behavior, respect, and knowledge they need to move on in school. The stories are shocking, funny, sad, and sometimes depressing. Anyone who thinks the job is easy, or that they are paid too much, or that they get too much time off or that all the incoming kids and parents are the same in every school is sadly mistaken.
Sorry about the rant...back to hoops.