It makes sense to have students evaluate their teachers within reason. Obviously, kindergarteners aren't going to provide a lot of detailed feedback and "difficult" teachers are going to get harsher reviews than the teacher who gives every kid an A.
Any system of evaluation would have to understand the limitations of student evaluations, but it is good to get as much information as possible to understand what our teachers are doing. If the evaluation gives kids a chance to give examples of the way a teacher helped them, or state problems they had it could help the teacher learn how to be better. It's at least better than just judging teachers on test scores.
Students have always been the ones getting evaluated and graded. If they received a low grade or score it was assumed it was because they hadn't learned, lacked enthusiasm, was lazy, or unable to comprehend the subject. It was never believed to be that maybe the teacher was below average. By grading the teachers, this would give the school administration the information they need about their teachers. Most teachers receive their raises and promotions dependent on their years of service, but with a grading system in place that could help make sure that the best teachers are being compensated. The school administration and school board are not present in the classrooms and have no real idea how well the teacher is performing or how they are perceived from their students and their parents. A grading system would allow them to know this information without having to sit in every classroom. Knowing that they will be graded might just be the incentive some teachers need to step up and perform better.
No because if students evaluate them it could show why they hate their teachers or even how bad they are and it could just be a bad influence. Also, why should they if your so worried you should just come to there class and see or have a note sent home on their teaching