OP I think you need to speak to the school but I would suggest that you write an email first so that you have a written record.
Try to stay calm and keep it brief.
Explain what happened in a couple of sentences.
When my DD was collected from school on X date and time she had bite marks on her face and scratches on her arm. We were not asked to sign the accident book or properly told what had happened. It has since been confirmed by DD and another student that X has bitten and scratched her.
Then ask them what you want to know.
I would like to know how this was allowed to happen and why it was not properly recorded by the school at the time. I would like you advise me on the school's policy for dealing with this sort of incident and what you intend to do in the future to ensure it doesn't happen again.
Then arrange a time to speak to them.
I am at work and my mother collects my DD, so unfortunately I cannot discuss this in person, however I would like to arrange a time to telephone the school and discuss the issues I have raised. Can you confirm if the appropriate person will be available at X time on X date to discuss this with me by telephone.
Then in the conversation reiterate your points, what you want to know and what you want them to do.
Confirm what has been said in another email, so you can't be fobbed off later if you have reason to raise the matter with them again.
You and your DD have my sympathies. My DS was bitten on his face, arm and hand by a girl, and was badly scratched as well. She made an absolute mess of him in a matter of seconds. He was cut and bleeding in several places and the bite marks and scratches on his face ended with a black eye. He still mentioned it months later so it was a long term upset for him. He still, three years later, has a small scar on his face where she bit him.
He was distraught, needed first aid treatment, and her family were very dismissive about it as "biting is what kids do" and "she does this every time we go out, but what can we do, keep her at home all the time?"
No, but they could and should have been supervising her. Instead they were sitting in a place they couldn't even see her, completely unaware of the injuries she was causing to three different children including a baby, until the staff alerted them to the trail of blood, crying children, and angry parents making complaints about their child.
They told her she was naughty and then hugged her when she cried about it. 