The first teacher who saw the clock told him not to show it around. They definitely knew it wasn't a bomb. It's not even that hard to have some sympathy for the teachers or even school administrators who are subject to all sorts of stupid policies. The insane thing seems to be that in the entire chain of escalation from teacher to principal to police nobody appears to have thought of some better way to resolve the situation than handcuffing a 14 year old at school and carting him off to juvie.