Do you think I could sue and win?

I took a course at a trade school that ended two months ago. I have always gotten along with my superiors but this teacher was not meant to be in a clroom. She spent 90% of the time telling us about her personal life and the other 10% giving out hand-outs. On multiple occasions she would get snappy with students who tried to voice their opinions. She would constantly accuse us of talking behind her back. I turned in all homework and never missed cl. I took the final exam and ped. Now two months later she said she is holding my certificate until I come back and do another in cl project. Multiple people have already complained to the school about her and now this has happened. I don't think it's right or legal to make someone come back to cl two months after it's finished. What do you think?