ONE OF THE LAST survivors of the War on Poverty is slated for extinction. The president's budget for fiscal 1986 and beyond would close down the Job Corps, one of the few programs that has ever succeeded in realistic measure in dealing with the nation's hardest-to-employ youth.

Like most social experiments of the 1960s, the Job Corps was conceived with an excess of expectation and a deficit of common sense. Unlike most social experiments, the Job Corps was allowed to survive long enough to learn from its mistakes. When Richard Nixon proposed ending the Job Corps, management was poor, discipline was lax and some sites suffered from racial discord and vandalism. As William Mirengoff, who took over the program for the Nixon administration recalls, "The media blew up every fistfight into a storm of violence."

Job Corps' administrators recruited counselors who knew how to deal with street kids, tightened up standards for counselors and youths and got unions and businesses to update training courses. A few years later, careful studies showed the Job Corps scoring impressive successes in changing the lives of kids otherwise headed for disaster -- those with arrest records, out-of-wedlock pregnancy and truancy, for example, in their backgrounds.

The Jobs Corps is a residential program. It takes youths out of ghettos and depressed rural areas and moves them to camps to do conservation work and training. The hope is that the change of atmosphere and routine will make it easier for them to shake off the bad habits. That makes the program expensive -- $15,000 for a year-round slot. It also means that the initial dropout rate is high, since many can't make the adjustment. But it also accounts for the program's notable success in increasing employment, military enlistment and further education, and reducing criminality and welfare dependency among the those who stick it out.

In making its case for disbanding the program, the Office of Management and Budget focuses only on the high cost per slot -- ignoring the fact that more than one youth can fill a slot during a year -- and the relatively low rate of direct placement in jobs -- ignoring other positive outcomes such as military enlistment or return to school or the fact that, as in most training programs, large numbers of graduates find jobs for themselves. But controlled comparisons (which don't make all these obvious mistakes) show that the Job Corps is a good investment for the taxpayer. And even those calculations don't take account of the moral returns to a country that reaches out to its most disadvantaged young people.