the other day, on a spur of the moment desicion, i pulled out one of my slings and handed it to a freind of mine, when he asked what i was doing, i told him that i was teaching how to use a sling.  because we were in the cafeteria of the school before classes started, i also pulled out my hackeysack to use as ammo.  i showed him how to load the sling, and after several failed attempts at trying to fire the projectile, he was starting to get a little frusterated.  when the cafeteria kitchen's big metal door slid open, i walked towards him, as he was focusing on loading the sling, and starting and overhand windup.  i was standing right in front of him at that point, and just as he was looking up and swinging the sling, the hackeysack came crashing down on my collar bone.  it's a good thing that we were using a hackeysack, because if we had been outside using rocks, i might have a fractured collar bone, or at least a nasty bruise.  in fact, i really didn't even feel it that much, so i was pretty lucky.

I think most of my teachers wouldn't know what a sling is.

Its not metal. It's not sharp. It's not an explosive. Therefore, it's not a weapon. This is the attitude of non slingers until they see one in action.