How would you handle this?

So, my girls just started a preschool today, it's highly recommended and has video cameras in ever square inch of the place, my sister has helped run the facility for years, so I trust it. Anyways, to my point, today was the first day and my 21 month old was bit three times ? apparently this was unprovoked (I made sure) and one of them is on her face! I'm livid. Like so livid. Nobody called me to tell me. I called around 1PM and they said DD2 had an incident and her friend bit her but it wasn't bad and didn't break the skin. So I told her that was ok, kids bite and I understand because DD2 bites DD1 occasionally. When DH picked them up there were two more bites (that we weren't informed about) and the ones on her face and leg broke the skin. I'm trying to rationalize this and be reasonable but I just can't. I'm angry. They said the boy is teething and is usually extremely sweet, they called his mom to pick him up and that tomorrow they would pretreat the teething and hope it didn't happen again ? I'm new to this, I've been a sahm for over three years now. How would you handle this??