A teacher murders an entire group of students to teach them a “lesson” about how to behave in class. In taking the idea of corporal punishment to an absurd, violent extreme, this gruesome fantasy makes a serious point: there is no role for physical discipline in the classroom. For one thing, the poem implies, corporal punishment is cruel. For another, it’s ineffective: after all, when “the carnage” ends, there are no students left alive for the teacher to wag his “finger severely” at—that is, there are no students left to teach!