If you could add more details to your question it would be helpful to answer. (Of course, you are not obligated to do so) Is the teacher touching a student in anger? To help? Simply placing a hand on their shoulder? Touching in an inappropriate manner?
If a student feels uncomfortable about anyone touching them inappropriately or in a manner that makes them feel unsafe they should go directly to the school counselor, nurse, principal and/or tell a parent. If a student does not feel that they can talk to any of those people, then please call the local police department or social services agency and ask for assistance. These agencies are equipped to help students during difficult situations, including feeling threatened by someone else.
However, I need to reiterate that knowing the context of your question could help us to help you.
Louise Masin Sattler NCSP
Nationally Certified School Psychologist