The whole thing sounds like a tragedy, and I really feel for the kid and his family. I hope the best for him.
That said, looking purely at the question of damages: not that there's any legal relevance to common sense, but the common sense side of me asks a basic question: did the kid not see the wall there?
I played in several gyms during junior high and high school ball where the back wall was just a few feet past the baseline and unpadded. You changed your play a little with that in mind to avoid hitting the wall. It was just common sense to prevent injury. My high school gym was like that, and did eventually put up some padding, which is the right thing to do. But, until that time, we played, played hard, and just took some basic precautions to not hit the wall!
Just to reiterate: the above 2 paragraphs regarding the question of liability (again, not being a lawyer, I look at this from a common sense point of view which probably has no legal relevance) do not detract from my sympathy for both the injured kid and his family!