Prior to 9/11 (because no way would this have been allowed to continue in this nu-Islamofacist world), at my high school during two semesters, someone kept calling bomb threats. They'd evacuate the school to the track field and let us go home early. This happened like 10 times. One time they did it and snow was still on the ground, and since the student populace was virtually a mob of faces, they realized they could get away with pelting the assistant principals and teachers with hard ice snowballs. A couple of faculty members got bloody noses. They really hate the bomb threats after that.