Why didn’t the student press criminal charges?
It’s hard to press charges when the assailant is a minor, and the Prosecutors refuse to charge him as an adult.
The impression I got was that he offered a deal. Apparently there were no witnesses and the school closed ranks around the attacker (go figure). In the end, they offered to pay all his medical expenses if he didn’t make a lot of noise. They are still paying his [extensive] medical bills.