Basic training began last week at Aberdeen Proving Ground for 115 new young enlistees, who'll follow the military regimen for five months to learn the lessons they missed in civilian life. They're the first class in Operation Challenge, which mobilizes National Guard members to teach high school dropouts the academic and job skills, and the positive attitudes, that will give these youth a running start at a second chance. Nationwide, the residential program aims to train 2,800 teen-agers in 10 states, through a $44 million federal program that includes a post-graduation grant for further education plus a year-long mentoring relationship with a Guardsman. Military discipline has proven effective in turning around the lives of many youths in trouble and unable to cope with traditional schools. So the concept is appealing as a barrier to problems caused by dropouts. Today's downsizing military also requires recruits to have a diploma. Teens admitted to the APG camp must be drug-free and not in trouble with the law, nominated by a community figure, and screened by a selection panel. The program is voluntary; no real troublemakers need apply. These criteria help to select the best of the at-risk dropout pool, all but assuring its success. But it raises a question why these select teen-agers could not achieve success at home, under the wing of the role models who nominated them. With all expenses paid, a weekly stipend, and a $2,200 fellowship at the end of five months, the program has a potential for making it appealing to drop out of high school. The cost is $13,500 per youth. One benefit is that National Guard members will find jobs working with youth in the program, helping the teen-agers to get a high school diploma and directing the military-style daily routine. Vacant Guard barracks at APG are being used. As the active armed forces reduce their numbers in the aftermath of the Cold War, the National Guard in Maryland and other states is looking for new non-emergency tasks to perform at home. The dropout camp is one of several such pilot public service programs authorized by the president. Given the public costs of providing for those who fail to finish high school, this boot camp approach could prove cost-effective without committing graduates to enlistment in the armed forces. The youths have failed in traditional schools, but they volunteered for this regimented alternative. They merit this chance, as does the National Guard.