Why did the nurse check David's face and injuries?

In Chapter One, the nurse examines David as soon as he arrives at school. When she asks what happened to his eye, he tells her he ran into a door, but she reminds him that he used that excuse last Monday. He then changes his story to say a baseball bat accidentally hit him, but the nurse knows better, and as usual she gets him to confess. The examines him thoroughly and points out an old scar on his stomach, asking if this was where his mother stabbed him. Dave says yes, and then feels like he has done something wrong. The nurse is noting the abuse that David has experienced, so she can make her report and call the proper authorities.