Ignorance that was likely being exploited for political purposes. As in, his father probably encouraged his son to do this. The father knew that it would likely cause someone to freak out, student or teacher; that it beeped helped and even better that it was in a metal case. There was no reason to bring the item in, let alone a the week of 9/11.
The school admins reacted as stereo typically badly as they could have hoped. It should have been assessed quickly and immediately removed from the school. Instead it just got stupid quick.
So this father will now get images of himself with his son with our President. We get some immediate attention to the horrible plight of Muslims in America (there isn't any horrible plight other than some people don't trust them)....