Ashley, I think when you have a bad field expereince you should let your supervisor know as soon as possible. Maybe talk to your cooperating teacher. Maybe she does not realize what your duties are in the classroom and if you tell him/her that you would like to get more invloved then they may let you. I would just say do not wait until the end to say something. Speak up, so maybe things can change and it will not be a waste of your time!
I am glad to hear that you did have at least one good experience!!
Also, I promise that no matter how bad the experience may seem, it is never a waste of time being in the schools, this is from a secondary person who barely got any exprience in a school and is on her way to student teaching...take advantage of every moment you have in the schools!!!