Why administrators can't always trust students

I've seen a lot of discussions lately talking about the pros and cons of having teacher evaluations.  Personal thoughts:  I think that student evaluations should be done. I think that we should look over evaluations and consider carefully what students have said and why they may have said it. As my boss always tells us when he hands out evaluations, "Let’s remember that even the best surveys tend to provide us with something that we need to think about." At ITESM teachers are graded on a scale of 0-5. 0 being perfect and 5 being... not so perfect. We are expected to get an average of under 2. If we are over 3 we need to seriously re-evaluate our lessons.   However, as far as administration goes, I think that evaluations should, indiviually, be taken with a grain of salt. After all, as the comic humorously shows what the administrator sees is not always an accurate depiction of the class. I do not think a teacher should be given a raise because or good evaluations nor fired because of bad ones. If anything, the evaluations may provide a reason for the classes to be monitored so an administartor can see what is going on first hand. If interested you can check out some of my past student evaluations here and here What do you think? Are student evaluations a valuable tool or simply a way to reward the "cool" or "pretty" teachers.