Try to be proactive. Before they get to you, let an administrator and if your are comfortable, your teachers know what is going on. That way, the teachers can keep their eyes open, and the administrators can intervene before something happens.
One thing to consider is the 'snitch' factor. You probably don't want the other kids knowing you told on them. If you're worried about that, talk only to a teacher or guidance counselor you trust, and ask the teacher to go to administration for you.
Another thing you can do is avoid these people. Figure out when they're in the halls and don't be in the same hallways as them. Be very aware of your surroundings so you can turn a corner or duck into a supervised room on a moments notice. You may need to be the first one out of class and get to your next class quickly, or be the last and take a route the other kids don't take. If you have a friend who is in the same classes, walk together and both of you be aware of the people near you.
Students should feel safe in their schools. There is legislation requiring your school to take steps to ensure YOUR safety. Let the school know what's going on so the staff can do their jobs.
Good luck...
