Last year, a third grader at Kris Christensen’s school in St. Paul, Minn., was hospitalized. She had been thinking about suicide. Her problems were mostly invisible to adults. She had been sobbing alone in the bathroom. And unfortunately, a student has to cry for help loudly—noticeably—to get the attention of overburdened school mental-health professionals. Just imagine: this 9-year-old child easily could have slipped through the cracks. “The kids who are quiet, who are more internalizing—they don’t get their needs met…