Juvenile injustice: courageous probe of ineptitude; The Child Savers, by Peter S. Prescott. New York: Alfred A. Knopf. $12.95.

"The Child Savers" is a cynical title for a book exposing the incredible legal and human chaos within New York City's juvenile-justice system. Far from saving helpless children from brutal abuse and neglect or rescuing and rehabilitating them when they break the law so they will not grow into hardened criminals, the Family Court is so cruelly inept that in many cases a more appropriate title would be "The Child Destroyers."

A little boy, savagely tortured and burned by his parents, is returned to them. They are found not guilty. The next word the child's social worker gets is that they have killed the child. She is shopping for a blouse. Suddenly, in the store and among strangers, she screams. It is all so unjust.

Seventy-five percent of all abused and neglected children are returned to their homes, the older ones after having testified against their parents in court. And while such cases have soared to epidemic proportions in New York, as elsewhere, this court has cut its social work staff in that bureau from 15 to 6.

Often, juveniles who have committed the most violent crimes including murder, and often more than once, go free, while children who have committed minor offenses are incarcerated. At one detention center, known for its inhumane conditions, the newly arrived children were often beaten and raped by other immates and subjected to alcohol and drugs, as well as beaten and put into "can't win" situations by the staff.

This center was closed thanks to a lawsuit filed by the Legal Aid Society, but Michael J. Dale, head of the society's Juvenile Rights Division, special litigation unit, asks: "What are the other facilities like?" It is a haunting question.

Peter S. Prescott, a senior writer and book critic at Newsweek magazine, broke through the walls of silence. He waited out a whole year of delays to get permission to be on the premises for months at a time during the six years he spent on the book. His technique of not preaching but letting the stories and interviews speak for themselves is extremely effective.

We meet unqualified, capricious, stupid judges, whose temperamental and unfeeling behavior we can scarcely believe. We see indifferent lawyers who are in it for the money.

But even in this nightmare, Prescott finds dedicated people genuinely concerned about the best interests of the child. They are just too few, and the odds they work against are too enormous. Michael Daie represented a child with aphasia for 2 1/2 years and appeared in court 36 times before 18 judges to get the child placed in an appropriate setting rather than with children who had behavioral problems.

Judith Levy, considered the toughest and ablest of the corporation counsel attorneys, says: "I do care. It's a career. It's not just a job. . . . I take work home with me. Every precinct in the city that we're involved with has my home number. They sometimes call at 2 in the morning."

Still, the overwhelming consensus among those Prescott interviewed was that it is hopeless, and the mood is one of despair.

Can anything be done? There is a trend toward getting a merit system for the selection of judges -- that would help. The New York Legislature is considering a merger of all its courts, which might bring about needed improvements, but the state's Supreme Court justices oppose any move to include the Family Court.

Charles Shinitsky, attorney in charge of the juvenile-rights division of New York's Legal Aid Society, is a lone voice pleading for time. It was schinitsky who, 20 years ago, was almost single-handedly responsible for bringing lawyers into the court to represent children -- the most fundamental change in the history of juvenile law. Until the US Supreme Court ruling "In Re Gault," children were chattel.

Shinitsky says this new system, in operation only since 1962, has been subjected to immense pressures and complications. "Let's make it work," he urges. "It hasn't been given a chance."

If the public is not to be indifferent, and to cease driving its troubled children into crime and despair, a way must be found to show that these youngsters are not "out there" in an alien world but that they belong to all of us.

If ever Americans can be made to care enough about their plight, Prescott can write another book entitled "The Child Savers" for which the title will be true.