The poem opens with a small joke: a voice urges someone to get up for school, and the reluctant sleeper turns out to be the teacher. From there, we're inside his head during one dragging class. He keeps looking at the clock, then at the students, then back at the clock, and the time barely moves.
What he feels is a mix of boredom, resentment and self-pity. He thinks his own words are "dead," the essays are a "tower of incompetence," and his students seem like future prisoners he's only babysitting. Raised hands look like fascist salutes, which shows how irritated he is. Even their pimples make him think of the teenage experiences he missed.
The mood is darkly comic and weary. The repeated "He looks at the clock" makes the minutes crawl, and the last line, the hangover, hints that some of his misery is his own doing. His contempt is harsh, but it also seems to cover his own sense of failure.