Cancelling a Teaching Contract After You've Signed But Before You've Started Working

This is a sticky topic and you'd better have a good reason for getting out of a contract after you've signed. If there's a real family emergency, that's one thing, but if you want to get out of a contract and take a better job that's another. If you give enough notice it might be easier on the school than if you try to get out of a contract last minute.
Many schools have you sign letter of intents and then offer you a contract later. If you've signed the contract there are usually two situations: you're in country or you're not.Here are what some people have said at ISR about getting out of contracts. Most people say that it's ok to back out of a contract.Some people say that if you used a recruiter or went to a job fair you will have to pay for the school to find a replacement and might be blacklisted.
In Country
If you're in country and plan on accepting another job in country, make sure there are no legal issues involved. Some employers might threaten to take you to court. Find out if they can do this. You're better off trying to talk to your employer and get out of the contract without problems.
If you're in country and planning on accepting a job in another country, you should have less problems.
If they've started getting you a visa or have already gotten you a visa, call immigration and ask what to do. Some countries require a letter of release or permission from the employer to leave the country.
Not In Country
If you're not in country, there's probably little they can do. You might have issues in the future getting a visa from that country though. Contact the consulate or embassy for more information.

Blacklists
Some people say they exist, others deny it. To be sure, administrators talk to each other, so be careful about pitting schools against one another in hopes of getting a better job. You wouldn't like if a school suddenly backed out of a contract, so try not to do that to a school.