On what grounds would you sue him/her?
This sounds a little silly. I think we need more details.
It's a common misconception that anyone can sue anyone. You do need a reason, believe it or not. Sure, you can try to sue whoever you feel like suing. I could try to sue you for taking up my time with this posting. I could say that I'm worth $45/hr, and this took me 30 min to read, respond to (including spell check
and editing), and so I'm suing you for $22.50. But it'd be nearly impossible to find a lawyer willing to take the case, and even harder to find a judge who wouldn't throw the case out without hearing it.
If you want to sue because you got a bad grade, it's not going to work. Descrimination-probably not either, unless it was not only very direct but also had lasting negative effects to your life, health, etc. Did she stab you with a syringe full of heparin and you bled for days?
This was way too vague. We need some more details before we can offwer you any type of information or advice.