A news station actually named the device, which I've blogged about before.
The video gives a ... somewhat accurate image of such device. A "works" bomb is technically a pressure device, a container which ruptures from "mild" pressure buildup due to gasses produced from a spontaneous chemical reaction. As opposed to the sudden, violent pressure buildup generated by flash powder after it has been ignited.
They call the devices "extremely dangerous", perhaps a little bit overreacting there. Such devices don't generally create much of an explosion, as pop bottles do not stand up to a lot of pressure, but they do -as mentioned in the video- hurl caustic chemicals in any direction upon rupture, danger depends entirely on the nature of the chemicals used.
The kids mentioned in the article/video will be facing serious charges ... they should!
I personally like tinkering with "high energy chemistry" too! But I don't put other people at risk doing so. The safety of those around me and my own safety come before anything! These idiots left dangerous chemical devices lying around school, does it get any worse than that?
As for an example of how to toy around with these devices in a safe, I'll refer you to Spatula Tzar, who explodes such a device in a highly ontrolled way, nine feet below the surface of the earth.
Raise your kids! Pay attention to them!