Can they say such a thing if it isn't true and documented?

I applied for a custodial position at a elementary school in lake worth fl. I was granted an interview with several people that worked at the school, I was told that they would be in touch. I get a call from the school, the principal wanted to talk to me. She asked me questions regarding my employment choice and a few about myself. She saw on my resume that I've worked with kids before and went to college for child psychology as well. She asked me to step out for a few minutes, she calls me back in and offered me a position working in the school as a behavior interventionist. I accepted the offer and waited for my next interview. The next week, I get a call from the school, they want me to come in. She told me spoke to someone from my old employer, oakdale high school. She was told that I have "personality issues" and because of that she can't hire me. I lost out on an opportunity to work with kids due to an untrue undocumented, vindictive comment. My ex employer is in Frederick MD.