I would expect that minor cosmetic damage is not something the school is going to be concerned about. Nothing stays looking like new forever especially when owned by a teenager. If the item actually BREAKS, that's when the insurance would kick in. Confirm that if you want to cover your bases - if the school is going to charge you if there's a scratch on the case that doesn't affect the function, that's the kind of thing that would make me reconsider. But that would indicate that the school is in this to make a profit not as an educational experiment - wouldn't be the intention to expect the students not to put a mark on them. Especially if they want the students to actually carry them around and use them all the time, rather than leaving them in a box in their room.