Bullying by Administration

My son goes to Hempfield High School in Greensburg PA. We moved here last year because the school was received one of the highest ratings in the area. My son 15 white man and high school student has suffered serious bias and prejudice this year. Most of his friends are underprivileged African American students in a predominantly white school. He has teachers yelling at him in front of the whole class things like "I know who you are and where you come from" what??? The 12th grade Principal, who I feel is the bully has even called parents and told them they should keep their son away from mine saying "he's trouble". Both of these items are documented as I was very upset and had numerous conversations with the Superintendent. The Superintendent required the Principal to apologize to both my son and myself for the phone calls. Ths never occured and the Superintendent was notified several times and still nothing. The teacher did apologize and admit he was wrong but there was no discipline