Do they have a case against me if I change employers?

My former employer (school) gave me a contract which I signed but when I was given a copy, the employer refused to sign. I then found out my wife was pregnant and under the contract that my employer refused to sign the amount and most importantly the insurance they offered will not allow us to financially take care of our new responsibility. Also, I just received a bounced payroll check from my employer (something that has happened to other teachers at our school more than once). This adds another financial worry to the equation. Another school offered a position that meets my financial needs as well as they signed the contract without refusing. I told my vice principal and other teachers. All I said was that I made the right decision, but the principal threatened legal action. The school has a month and a half to find a replacement.