I had to refute my rating one time. I have always received exemplary ratings, but one year, a new administrator evaluated me unfairly. He said I had written too many referrals. This is what I did. I did take the advice of my union rep, and that advice was to arrange a meeting with my evaluator, show documentation that could prove otherwise, and ask for a re-evaluation. So, if you have documentation of other appraisals, or if "non-observable" criteria played too much of a role, he/she cannot include this. For example, my evaluator could not document in-class behavior problems and I presented him with documentation that proved I had indeed followed the steps of behavior intervention-student conference, parent calls, counselor referrals, parent conference, and so on. I had done this admin a favor by allowing some students that another teacher could not handle into my class. I reminded him of that as I also showed him my previous appraisals. It is best to try and work things out with the appraiser first. They WILL appreciate this. Be professional and if that doesn't work, keep documenting, and if your appraisal is truly unfair, then contact your rep for a meeting with administrator. Do not worry; if you have one sub-par appraisal, it probably won't affect your career too significantly. Hope that helps.
If you belong to a professional organization for teachers, contact their legal department. If you don't belong, join next year. With some of the parents I encountered and the lack of administrative backing, it was helpful for me on several occasions. In Coweta County, Georgia, you can attach a written statement defending yourself or providing a rebuttal. Check with your county/state educational evaluation coordinator for information about a written defense. Unfortunately, after 35 years of teaching, I had a couple of incidents with a new, over-ambitious administrator. My county provided for a county evaluation of my abilities as a teacher after the in-school evaluation was one of "needs improvement". There should be some sort of procedure that can protect your teaching status. Good luck on your findings.