My Grandson is being bullied

My Grandson who is 13 in 8th grade is being bullied in his Junior High School. He is emotionally sick from it and we just found out that this has been going on for months. He is a great kid and on the wrestling team at school. He is afraid for his Mom to tell school officials because he doesn’t want the bullying situation to get worse which it will. They are putting their hands on him, throwing things at him and pushing him in hallways. What can we do to help him????