Guys, I need an advice please. On the Edjoin.org they put a vacancy for only Math position. I was hired as a math teacher in CA high school and I only had Full Math credentials at the time of hiring. My first year evaluation was excellent. During my second year I added physics credentials to it out of my self interest. So during second year school added physics class along with regular 3 math classes. They never had any Physics teacher prior to me. So I am the first Physics teacher at that school.My second year evaluation on "MATH" was also excellent. I was given the tenure. However I lost interest teaching physics the third year which is this school year. So I told my principal about it and said that I wanted to continue to work as math teacher as hired. They said that I did not have the choice and that they have the right to assign that class to me since I had physics credentials. I was shocked. I didn't say anything and quietly left the room.I am currently teaching Physics(not my choice) and Math. Why should I teach Physics when I was not hired to teach that subject in the first place? Even my contract doesn't mention that I was a physics teacher. Can I revoke my Physics credentials to avoid them giving me Physics class? Does that affect my job? I am planning to talk with the union. But I also need your valuable opinion--Thank you.