First period, 8:45 am, a circle of high school students sits so quietly that all you can hear is the whirl of computer fans. Today’s lesson: attention to breathing. “Just notice your breath,” says the instructor, Satyani McPherson, “where it manifests in the body and the abdomen. … And whatever is appearing, just allow it to be there.” A student walks in late, and the door slams. No one moves. Eyes are closed. Fourteen chests