What can I do if I feel like I'm being harassed at work?

My superintendent called me today and told me that a person using one of my school offices possibly needed to move. She asked me to not let him know yet. The person was my friend and therefore I let him know that he may be moving. He got upset and called the district office and then I received a phone call from the Superintendent needing to talk with me. She began yelling at me and telling me I was the worst person she has ever worked with and that this was the last straw. I told her that her yelling was unprofessional and I did not appreciate her attitude towards me. She said "you're done" and reassigned me to my trailer house, on district property, and made me turn in my keys to the school and told me that if I needed to be available during work hours and if I needed to go somewhere I needed to inform her first. She has embarrassed me in meetings and even told me to shut up in front of my fellow workers. I did not reveal any confidential information but she wrote me up for being insubordinate and unprofessional conduct. What can I do? I feel deflated and embarrassed as well as stressed during the year from her constant disrespect for me.