Have you tried talking with the principal regarding your concerns about the school? He or she should be made aware of any issues with violence or unsafe conditions on campus, and can share what is being done to protect children and address problems.
Additionally, you should talk with the school district about their policies with regards to transferring from one school to another. If your daughter attends a school in the United States, you can use SchoolFinder to find the contact information for the district, as well as to review information about other schools in the district:
http://www.education.com/schoolfinder/
If you do decide to switch schools, there are some things you can do to help ease the transition for your daughter. Here are some related resources...
Transition Points: Helping Students Start, Change, and Move Through the Grades
http://www.education.com/reference/article/Ref_Transition_Points/
The Parent's Guide to High School
http://www.education.com/grade/high-school/
Teen Years (13-19)
http://www.education.com/age/teen-years/