Do we have a personal injury case for my son due to negligence on school property?

My son slipped on ice right outside the entrance doors to his school and dislocated his knee as well as sprained it. Prior to his incident a teacher also slipped and instructed the door monitor to get the area salted immediately, this was not done, hence the fall made by my son and other students. There is a school accident report and witnesses to the fall. He had to be taken to the school clinic in a wheelchair and I had to bring g him crutches to use for the rest of the day, He had to go to the ER as well as his orthopedic doctor as he previously injured the same knee he fell on last year. The doctor said due to the continued injuries to this knee he might have to undergo surgery to better mobilize the knee from further damage. We are waiting approval for a MRI to determine the extent of the damage. There were many students complaining about the lack of safety on the walkways and parking lot. There was black ice patches everywhere. No care was taken to safeguard the staff and students. It is also my understanding that a student broke their arm by a fall on the ice. I believe this can be considered gross negligence since a teacher did instruct the door monitor to get the ice taken care of and did not. The Vice Principle was at the scene of my son's fall and asked if he was alright. I too e-Mailed the Superintendent, Principal and Vice Principle of the occurrence and how upset I was about their negligence to keep our children safe and have not heard anything back. I wanted someone held accountable for not keeping the school property or grounds safe for our students since the weather was horrendous.