I call parents strictly from a medical standpoint.
Nurse: Maam, your son was in an altercation this morning, he sustained an injury to his left eye. I have checked his vision, clear, pupils reactive to light. he does have some swelling and discoloration around the eye for which I have applied ice. I suggest you keep an eye on it.
Mom: Who did it? is the kids punished what is the school doing about it?
Nurse: maam, I can only speak to you about the medical needs which were addressed, if you like I can transfer you to the vice prinicpal (or security officer, principal) to speak about the disciplinary issue.
Thats all I say.