I don't know the legalities so I can only pass along the experience of
Teachers in hard to fill positions were not allowed out of their contract
and had to finish the year. The elementary teachers I have known in your
position, easily replaced, were released. Current super is more
hardnosed and holds people to their contract. So, I do think it is a district
by district proposition. Get a copy of board policy and read up on it.
Good luck to you!