Teaching on a different endorsement

    I would like to teach in an area other than the one in
    which I am currently teaching. My state department has
    added the endorsement and I'm ok to switch for the new
    school year. My principal will never agree to this, so I'm
    willing to leave the district; however, I do not not to
    leave without at first securing a job elsewhere. Can I be
    hired while still under contract? Do I need to resign
    first? How do I go about this withhout being faced with no
    job at all come next September? Thanks.