Just my 2 cents worth....
First of all, glad the boys ok.
Police report, immediately.
School outing is a great thing, but the teachers didn't handle the situation at all, from what I read. Teachers at a minimum need to be reprimanded and apologize for not taking immediate actions to see that the incident never happens again, that the wounds were treated properly, and the parents notified. If the teachers refuse, fire them.
The place where the outing occurs needs, at minimum, at letter from a lawyer. Possible law suit to follow if satisfactory solution is not obtained. Same for the owner of the dog, if they can be found.
Dog needs to be killed.
