First, remember that their is a difference between bullying and conflict. From the school system's point of view, they don't want to get in the middle of what might just be high school drama. But, if you show them how extreme this has gotten and that this is repeated targetting, then it is bullying. Your school should pay attention.
I was part of a bullying case involving a friend of mine who was getting severely harrased in high school. She eventually ended up suing the bullies for harassment, and she won. But, it was a huge battle for her. She struggled with bullying for years from upperclassmen in school and some of the "popular" girls in her grade. A lot of it had to do with who she was dating when she was a freshman, but it turned into a huge problem that lasted for about 2 years before she did anything about. Not suggesting that you press charges, but these are things that my friend wishes she had done so it didn't have to go so far.
1. Document every incident of bullying. Take screenshots, and print them out. Save all text messages on your phone. If it happens in school, make sure a teacher, guidance counselor, ect is aware of the incident. Always tell your parents, because they can always help you and they will remember the details of specific incidents that you want to forget. I know remembering is painful, but it will help lead to an end to the bullying.
2. If any sort of harassment is happening in school, they HAVE to take action or else the negligent people WILL lose their jobs. In Massachusetts, the law has been changed to say that any incident of bullying that happens in or outside of school is a school problem, as long as the students involved all go to the involved high school. So, if it happens on Facebook, Twitter, Formspring, texting, gym class, math class, school bus, parking lot, football game, party, ect- the school is required to investigate. I don't know where you live so these laws might not exist in your state, but it is important for you to know that bullying is a hot topic, and no school system wants to be held responsible for neglecting a bullying situation. So, don't stop with the Administration of your school. They know what they should do if possible bullying is in question, so if you persist and show the documentation to the school, they know that their is a problem that they must investigate.
3. If your friends see the bullying as well, they can help. I was the person that went to the administration and reported the bullying of my friend. And by then, my friend had been sexually harassed by upperclassmen, threatened to be killed, gotten food thrown at her, beaten up, and hospitalized for depression. Every time one of these things happened, she and her parents would go and report it to the school, and the school would ignore it because they thought she was making it up. When more and more people started reporting that they had seen this bullying, the school finally started to investigate, and found the huge problem. So, if your friends can vouch for you, ask them to come with you or go alone to talk to your guidance counselor, principal, ect.
4. If it gets really extreme, go to the police. They must take action if you report harassment, and most likely you will see some progress in stopping the bullying. Have documentation to show them, because they can't deny what you have on paper.
I really hope you can get through this. People are absolutely cruel in this world, but I promise, my best friend who was bullied in high school is now a happy, healthy, college student who is enjoying life and doesn't even look back!