My son got in trouble for yelling at a girl at his school

My sons teacher told me son son threw his book on the ground and yelled at a girl. He's 12 and has been coming home telling me about this girl who won't leave him alone and keeps chasing him around the play ground. I'm assuming this girl has a crush on him, but my son really doesn't like socializing with people that much. He said he had been telling the teachers to make her leave him alone but they didn't do anything. He was on the play ground trying to read his book and she kept coming up to him to annoy him and hug on him. My son absolutely HATES being touched. He said he told her to leave him alone him alone several times and to stop hugging him. He kept moving, she kept following him. He said he just wanted to read his book and be left alone. He told the teacher the girl won't leave him alone and keeps trying to hug him but she just told him to be nice. She he moved again and tried to read his book and the girl jumped on his back. He got her off threw his book on the ground and yelled at her to leave him alone and she ran to the teachers crying. I agree he shouldn't have yelled at her but no student should have to be uncomfortable. The teacher should have intervened when the girl wouldn't leave him alone. It's not fair that he kept asking her to go away. He kept moving. He kept telling the teachers until he finally got fed up with her touching him.