First, while I'm not sure about the inner workings of school metal detectors, but I know it's fairly simple to walk out of stores with security tags on clothing without setting off the detectors. It's not a difficult thing to do at all. Maybe this child was carrying his backpack the same way shoplifters carry their bags. Second, let's not go all soft and unicorn-y on this kid. Maybe he has anger issues, but he needs to be punished and severely. This "you poor child" attitude has got to stop--he made a choice, and he needs to face serious consequences. His parents or guardians, too.