Did the first teacher who asked him to just keep the device in his backpack "jump at shadows"? He knew what it looked like and was trying to help his student stay out of trouble. He didn't report him. Ok, so that's one "crazy" adult. The kid didn't listen.
Another teacher thought the same thing and asked him to put it away, and the kid didn't listen, again, and proceeds to set the alarm on the device. Only then they called the police. I guess, I don't see how brining this kind of a device, looking like a typical movie bomb, to a school in LA, NY (I don't know? think of the least "jumpy-at-shodows" area of the country) could have ended up any better without the police involvement. Heck, I am surprised the first teacher didn't report him and they didn't immediately evacuate the building.
Clarification: more than one American adult, where collectively some states/localities are more likely to jump at shadows than others..