Your link wasn't working... http://www.nbcphiladelphia.com/news/...115125844.html
I'm not saying I agree with how it was handled, but to some little extent I can understand. The school doesn't want any discretion whatsoever. They want their rule to apply to everyone, and then enforce it in a strictly yes-or-no fashion. This prevents their own discretion coming into play when deciding on punishments based on the type of gun: Nerf gun, BB gun, water gun, cap gun, etc. A discretion is just an opinion, and if the school makes their own discretion based off each individual case the results will be upset parents (customers), starts the elusion of favoritism/biasness, consequences become political decisions based on who the parents are, fear of being sued, etc.
It sounds ridiculous, but if the kid never got in trouble some parent would probably come out saying their child is traumatized and they'd end up suing the school because the school didn't enforce the gun policy strict enough thereby making their child nervous to continue going to school.
As far as my personal opinion of this story, I think the adults are the ones that need to be educated.
If only we could quantify "common sense" just like IQ...