As Ms. Davis stepped into her new classroom, not a single student paid her any attention. She set her purse down on the desk in front and looked around. All the high school students were either on their cell phones or talking to one another....

I can still hear them. In the stillness of the night as I wait for the grasp of sleep to take me, the sighs start flooding in from all directions. At first, they’re so low that I think I must be imagining them, but gradually,...