"Tried as an adult." The phrase rings with increasing frequency through America's courtrooms. In Michigan, an 11-year-old is charged with first-degree homicide in the shooting death of a playmate. A mentally disabled boy in Florida faces armed robbery and extortion charges that could bring 30 years in prison for stealing $2 worth of food. Faith in childhood, and its corollary that separate courts are required for children because they are developmentally...