FOR MOST OF the twentieth century, Americans' response to teen violence has leaned heavily toward reacting to it rather than preventing it. In the face of shrill headlines about exploding teen violence, government at all levels has tended to pour ever-increasing amounts of money into more police, more law enforcement hardware, more prisons, and more courts. Since the 1980s, expenditures in the United States for criminal justice (juvenile and adult combined) have increased four times as rapidly as for education and twice as rapidly as for health and hospitals, according to the Milton S. Eisenhower Foundation, which studies inner-city crime. There are hundreds of different laws, police strategies, and community programs to deter teen violence, but when deterrence fails the juvenile justice system takes over.

The juvenile justice system

The first juvenile court was established in...