You can sue your teacher and your school district for any conduct toward you that is violation of the law and causes legally recognizable damages to you.
The law compels no specific standard for your grade than that it reflect the teacher's judgment of your performance in the class. So it is not tenable for you to entertain ideas of a lawsuit about a grade.
Now, about the prospects for a lawsuit about unfairness. Again, unfairness can be the basis for a lawsuit only when the law requires a different standard of conduct than was done to you. What is the unfairness by your teacher and the district to you, other than the grade that you don't concur in? You didn't describe any other acts of unfairness, so it seems unlikely that there is any basis for a lawsuit by you against the teacher and district on this ground.
It is almost always the case that students must earn their grade in the classroom, not the courtroom.
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As you are an adult, now is a good opportunity for you to impress your teacher with your maturity in politely and reasonably discussing your grade with her. Don't immediately want to jump to lawsuits when a quicker, cheaper, and easier option potentially exists to fix your problem. If your calm conversation with your teacher does not satisfactorily explain your grade, you always have the option of talking to your school counselor or principal. You have not indicated that you have tried anything like this or why you think you teacher is treating you unfairly. Before you jump to conclusions about being treated unfairly, be sure that you have examined your own conduct and study skills and then talk to your teacher.
Along with the very good answers provided above, you would likely need to go through the uniform complaint process through your school district prior to filing a lawsuit. But I agree with the others, try talking with your teacher first with the help of your parent or guardian.