I understand your desire to join a sorority when you attend university. However, you have to realize that this question is inappropriate to say the least. We are not here to perpetuate any negative stereotypes to kids in high school. If you're asking about the validity of this myth, I would instead ask yourself why your teacher feels this is a relevant topic of discussion for class. I'm really shocked that someone in her position, and espiecially someone who's greek would say this.
I would go to the principal if I were in your shoes.