BULLYING IN PRIVATE SCHOOLS

My son has been bullied the past 3 years by the same kids at his school., physically, mentally and verbally. He intimidates him almost daily. It's to the ponint that i'm reporting an icident numerous times a year and to the fact that the headmaster has said that my son cannot return back next year. He has NEVER been in trouble or sent to the office, he is an honor roll student and won the Christian Characteristic award the year before last, but in all the 6 years my son has attended there- we had no problems ever...then this new kids started in K-5 and the bullying started. Not only with my child but several other parents have reported issues as well. But i gues b/c i report everytime i hear my son has been hit, they are tired of me reporting it and they have never, not once repremanded the other student for his behavior, even when it has been documented that another teacher saw him hit my son directly in the face. Please help me or point me in the right direction- please.