Hmm, I'd assume you live in a rather small town, considering the school consists of 50 students.
In your situation, it seems it would be preferable to discuss everything with your parents.
If I assumed incorrectly, and you don't live in a small town, moving schools appears to be the most practical solution. Smaller schools do tend to have less qualified teachers.
if not, and my assumption was correct, and the nearest schools are too inconvenient to travel to, at least have your parents speak to your teachers to resolve the issue.
As ReptilianKitten has said, you can show them you don't care, according to people I've met, they won't continue if you don't react.
You could also befriend the girl. I know that if I were in the same position as her, I'd be just as uncomfortable about it as you are.
