(TX) Does my husband have a case?

Location: Texas

My husband voluntarily resigned from his teaching position in April but continued to work out his contract. It was, as far as he knew, an amicable departure. He discussed with his principal why he was leaving. They had introduced a new method of teaching and while he had really tried to adapt to it, it wasn’t for him. (He’s taught for 26 years.)

He walked through the steps of voluntary resignation with HR and completed it. He then began applying for jobs in neighboring districts.

He was offered a job and accepted it a few weeks later. He’s been waiting on their HR to call so he can go sign the contract and bring them his transcripts. Yesterday, they rescinded the offer because, according to them, his last supervisor gave him a bad reference.

Is this retaliation? He has never had a poor reference before, ever. A lot of school districts say you have to put your last supervisor down as a reference, but he put her down even on those that didn’t require it because they had a good working relationship, he thought.

I’m not so sure we can prove anything. Any advice?