No, your local hardware store, or even a thrift shop. any electric start grill and some flammable liquid.
I find it entertaining when people who are ignorant on simple electronics try to lecture us non-luddites about technology.
When that clock in a box alarm is triggered it completes a circuit.
You add that to something like this:
and any flammable liquid and you have a bomb.
That part is 15 bucks at Walmart.
Attach speaker outputs to the switching mechanism on the igniter, when alarm sounds the circuit is completed.
I am not saying that was his intention, I am sure it wasn't. But, would you want the school to do nothing if they saw that thing?