My son was attacked at school today by two girls from his class. Here's what happened: during class,…

My son was attacked at school today by two girls from his class. Here's what happened: during class, he accidentally damaged another girl's project. He tried to apologize, but she got upset and wouldn't listen. The teacher saw it, and my son was threatened with a "D" (or equivalent failing grade). After class, two girls approached him in the schoolyard – not the girl whose project he damaged – and started threatening him. My son didn't quite understand how it happened next: whether he was pushed or hit in the face. He almost lost an eye; apparently, he hit his head on a metal shelf near the gate. The child is home, hysterical. There's a red mark from the blow near his eye, in the eyebrow area. It's unclear how severe the consequences will be. I've already messaged the class teacher, asking her to investigate and inform me of the actions taken. My question is: has anyone experienced this? Should this kind of injury be documented at an urgent care clinic or is a regular doctor's office okay? And what would you do in my situation? Should I go to the principal immediately or wait for the teacher's response?