How does one void an employment contract with a school district in South Carolina?

I haven't even taught there yet. The contract was for next school year('07-'08). Three days after signing, I received an offer for a dream job. I wrote a request to nullify the contract, but the school district I signed with says they will let me know when they fill the position before they release me. I don't know how long I can wait before signing on with the new employer. I cannot legally or ethically sign the new contract until I am officially released from the first one. Are they able to hold me in limbo like this? Do I have any rights that should allow me to void the contract? The district has over 3 months to find someone to take my place before the school year starts. This is a very reputable district. The subject is not a critical needs subject. The new position I wish to take is not a clroom teaching job. I'm not making a parallel move from one district (school) to another. This new job is MUCH more conducive to my personal and professional goals.