John J. DiIulio Jr. is director of the Partnership for Research on Religion and At-Risk Youth at Public/Private Ventures in Philadelphia. Gary Walker is president of the organization. They assisted the Council on Crime in America in drafting its new report, "Saving Children, Preventing Crime."

Today America is home to about 57 million children under age 15, some 20 million of them ages 4 to 8. The teenage population will top 30 million by 2006, the highest number since 1975. And the nation's two most widely respected criminologists, James Q. Wilson of UCLA and Marvin E. Wolfgang of the University of Pennsylvania, say that this demographic bulge spells trouble.

The criminologists are right. In 1994 along, there were more than 2.7 million arrests of persons under age 8 (a third of them under, age 15), and juveniles were responsible for an estimated 14 percent of all violent crimes a quarter of all property crimes and a quarter of all property crimes known to the police. There were nearly 4,000 murders committed by teenagers in 1995.

The increased use and availability of drugs has fueled the growth of drug-dealing street gangs. Most studies estimate the number of youth gangsters to be well into the hundreds of thousands. In some big cities, the percentage of juveniles in custody who tested positive for drug use has more than tripled since 1990.

Juvenile violent crime arrest rates rose 5.2 percent in 1987-89, 12.1 percent in 1989-90, 7.6 percent in 1990-91, and by at least 4.4 percent in every year hereafter until 1994-95, when arrests for violent crime amoung juveniles ages 10-17 fell nationally by 2.9 percent. But most criminologists think that dip is temporary.

When talking about crime and delinquency, liberals stress such factors as poverty and joblesness. The percentage of children under age 6 living in households with annual incomes under, $7,600 doubled between 1975 and 1994. Fewer than half of young black high school dropouts were either working or looking for work during 1994.

Conservatives, meanwhile, stress such risk factors as out-of-wedlock births to unmarried teenagers and child abuse and neglect. The illegitimacy ratio (percentage of all five births to teenagers, ages 15-19, that occur out of wedlock) rose from 29.5 percent in 1970 to 76 percent in 1994. And the number of substantiated cases of child maltreatment rose by 20 percent from 1990 to 1993.

Both positions are right, and related to each other in a downward spiral.

As U.S. Attorney General Janet Reno has stressed, the challenge is how to help these children--most of whom are concentrated in the most blighted neighborhoods of fewer than two dozen big cities--before it's too late.

Former New York City Police Commisioner William Bratton, whose innovative policing practices are rightly credited for driving dramatic drops in crime, has recently emphasized that while better policing is pivotal to cutting crime, "prevention has simply got to be a big part of the long-term anti-crime equation."

Bratton is a member of the bipartisan Council on Crime in America, which recently issued a report recommending three promising, community-based prevention strategies--monitoring, mentoring and ministering.

• Monitoring: This means community-based supervision of youth offenders, whether by professional probation officers or by neighborhood adults. Despite the passage of "get-tough" juvenile crime laws in many states, the majority of adjucated juvenile offenders get probation, not incarceration. Private citizens can help. A prime example is Philadelphia's Youth Aid Panel program. Panels of adult volunteers in each of the city's police districts hear cases of first-time juvenile offenders and mete out punishments that range from curfews to community service. The estimated receidivism rate is an impressively low 20 percent.

• Mentoring: Involvement by citizen-volunteers with at-risk youth benefits the youth to an extent that even some boosters of the concept might find surprising. Consider for example, the findings compiled by Public/Private Ventures in a study of 1,000 youngsters aged 10-16, almost all of them from low income, single-parent families, who participated in Big Brother/Big Sisters of America. The study found that juveniles matched with mentors were 46 percent less likely than a comparison group to initiate drug use, 27 percent less likely to start drinking, one third less likely to commit assault, and half as likely to be truant from school. The "Bigs" were not trained in drug prevention, remedial tutoring or family therapy. And, yet, by becoming a friend and providing support to these young people, these mentors cut youth crime and positively influenced young lives in many ways.

• Ministering: This refers to the work of local churches with at-risk youth. In New York City, for example, the Protestant but interdenominational New York Theological Seminary has trained more than 2,000 ministers who are presently providing to their communities a wide range of youth outreach services, such as literacy training and after-school programs.

But for monitoring, mentoring, and ministering to expand their effectiveness--and we need them to expand now --more citizens must volunteer. And they must get more recognition and support.

This comes about only when the rest of us adopt the "4thM" of crime prevention: a sense of moral obligation to American's children that transcends conventional political pontification and recognizes that getting warm-blooded adults into the lives of kids is the one sure way we have of saving our youngest, our most vulnerable, and potentially our most dangerous fellow citizens.