My son had a practical halachic question that stems undoubtably from his learning (by himself) mishnayos baba kamma. His class was playing kickball at recess and as he kicked the ball, it popped. As he put it, the ball was "meisa machmas melacha" (after all, he argued, the ball was quite dead). Is he chayav to pay the school for a new ball? I was about to tell him a katan is always patur, but that doesn't fly because he is over bar mitzvah now!
My son reasoned that he was a shoel, as the class had borrowed the ball for use at recess, and a shoel is chayav even in a case of ones. Sounds reasonable, but not so easy on his pocketbook. I helped him out a bit and suggested some other possibilities: 1) since he (or we) pay tuition for use of the school's property and materials, he might actually be a socheir, not a shoel; 2) since his rebbe was supposesdly supervising the class, the case may be one of ba'alav imo; 3) there is an implicitly mechila on the part of the school for these things otherwise they would be billing students for every broken piece of chalk, spilled milk at lunch, and other little calamities that are overlooked as par for the course of a school day (this is admittedly the weakest argument).
I told him to ask his principal, as I think the discussion he could have about applying dinei nezikin would be a real learning experience (not too many of those, unfortunately, in the school day). Anyone have any other sevaros on this one?