What should I do if my teacher is purposely failing me?

A few weeks ago I forgot to do my biology homework and now my teacher is failing me on all my tests and quizzes. I've compared them with others who got A's and each one should be an A also. But they are F's according to the grade she gave me. Recently she failed my final exam (again I checked). She has taken my grade from a B to a D. She is retiring now and only has to work here for another two days so I've basically lost the leverage of being able to get her fired or losing her pay for the week. What should I do?