There you are, in class, contemplating your hangover, listening to the professor explain the… There you are, in class, contemplating your hangover, listening to the professor explain the intricacies of the thermodynamics of the pseudo-Freudian imagery of whatever, and a tinny version of Kelis’ “Milkshake” song starts piping out of someone’s cell phone.

The student scrambles, embarrassed, to turn her cell phone off, and the class watches her rifle through her faux-Gucci to retrieve the beeping monstrosity. And the noticeably peeved professor just continues the lecture.

But a New York judge last week set a better precedent for dealing with such incidents. District Court Judge Salvatore Alamia sentenced a 17-year-old girl to 21 days in prison for contempt of court, after her cell phone rang, when the judge had expressly ordered cell phones to be turned off. The sentence will be served concurrently with her other sentence for criminal possession of a controlled substance.

“If you don’t know how to shut it off, go outside and introduce it to the heel of your shoe,” Alamia said. Props to the judge for taking a hard line on cell phones.

We all have social lives, work and family obligations, and mothers who call us at odd times to remind us to eat, but turning cell phones off isn’t too much to ask of people. Classes are for learning or napping or doing the crossword — for being quiet while a person whose salary you’re paying teaches something you’re interested enough to show up for.

Professors should take a hard line against cell phones, too — holding people in contempt of class, if you will. Cell phones are especially irritating during exams, and professors should consider docking points if a cell phone goes off during one.

All cell phones have a silent mode, and most have a vibrate mode — though the vibration setting is not synonymous with the phone being off. Having a phone rattle against the contents of someone’s bag, sounding like some crazed metallic cow, is just as distracting as hearing a midi file of “In da Club.”

The same rules should apply for people whose cell phones ring in theaters, especially during live theatre. No one comes to the cell-phone users’ workplaces and jumps up and down to distract them, so extend the same courtesy to the actors.

Clearly, the live-and-let-ring approach to cell phones isn’t working. Professors should set firm policies about phone usage and enforce them. Already, churches in Europe and, increasingly, in the United States are installing cell phone jammers, which block signals. These would not be necessary if people practiced a little common courtesy and, as Alamia so eloquently put it, introduced their buzzing, beeping, singing, vibrating phones to the heels of their shoes.