STUART SLAVIN, a pediatrician and professor at the Saint Louis University School of Medicine, knows something about the impact of stress. After uncovering alarming rates of anxiety and depression among his medical students, Dr. Slavin and his colleagues remade the program: implementing pass/fail grading in introductory classes, instituting a half-day off every other week, and creating small learning groups to strengthen connections among students. Over the course of six years, the students’ rates of depression and anxiety dropped considerably.

But even Dr. Slavin seemed unprepared for the results of testing he did in cooperation with Irvington High School in Fremont, Calif., a once-working-class city that is increasingly in Silicon Valley’s orbit. He had anonymously surveyed two-thirds of Irvington’s 2,100 students last spring, using two standard measures, the Center for Epidemiologic Studies Depression Scale and the State-Trait Anxiety Inventory. The results were stunning: 54 percent of students showed moderate to severe symptoms of depression. More alarming, 80 percent suffered moderate to severe symptoms of anxiety.

“This is so far beyond what you would typically see in an adolescent population,” he told the school’s faculty at a meeting just before the fall semester began. “It’s unprecedented.” Worse, those alarming figures were probably an underestimation; some students had missed the survey while taking Advanced Placement exams.

What Dr. Slavin saw at Irvington is a microcosm of a nationwide epidemic of school-related stress. We think of this as a problem only of the urban and suburban elite, but in traveling the country to report on this issue, I have seen that this stress has a powerful effect on children across the socioeconomic spectrum.