"We're in danger of losing our whole next generation," Nancy Reagan told the representatives of the National Federation of Parents for Drug Free Youth who came to the White House yesterday to meet with her. "We all have the same concern that drug abuse is one of the most serious problems our community faces."

To the carefully coiffed heads nodding in agreement, Mrs. Reagan said that "parents are the answer," and counseled them to be on guard against the ever-present danger of drug use among schoolchildren. "It does take time, being there when they come home, knowing who they're seeing, who's at the parties, will it be chaperoned? It's the most democratic illness there is," she told the mostly middle-class group whose children are, as one member put it, "meant to succeed."

It is "absolutely fascinating," Mrs. Reagan said, "to hear these young people talk openly and freely, with very little embarrassment of what happened to them, how they got started."

Yesterday, however, it was not the young who were doing the talking, but their parents. Some of them knew firsthand what the tales from the front lines sounded like; it was in fact the experience of watching their own children turn slowly into strangers that brought them into the fledgling organization in the first place. "Our experience was that if we'd had the information then we have now, we wouldn't have lost our child," said Marion McClatchy, a member of the group's board of directors from Rosemont, Pa.

Her son, she said, started smoking marijuana when he was 12. Not knowing what the reasons were for his sudden silences and gradual withdrawal, they took him to the family doctor and to a string of childhood specialists, thinking he was suffering from what McClatchy called a bad case of "acute adolescence." By the time he was 16, McClatchy decided that marijuana was the reason she was losing her son. He is 21 now, and estranged from the family. He and his parents do not speak.

"I don't think God lets these things happen to you without a reason," McClatchy said. "Now there are parents who come to me and say, 'How did you know, what did he act like?' And at least we can help."