I have a rule about cellphones in class: if one disrupts us by ringing, vibrating or sounding an alarm, the owner has to sing a song or bust some dance moves in front of the class. At first, this provision in the syllabus elicits snickers, but it’s no laughing matter. You need to be able to turn off your phones and pay attention, I say. On the first day of class, they shut off their phones. But it doesn’t stay that way.