It happened abruptly, with no warning, at a Chinese restaurant. We had ordered drinks, of work, when the resident 12-year-old looked up and asked: "What's PCP?"

PCP. Angel dust. Killer weed. The drug that sends its hallucinating users to psycho wards for months, the latest fad drug that is doing to today's young people what LSD did to my generation, a drug that some authorities say is more dangerous than LSD. PCP: the scariest drug around, and my 12-year-old is asking about it, casually, telling me he heard about it in school.

Parents these days know, if they have any sense at all, that their children are going to come into contact with drugs in school. We dread it, but we know it is going to happen. And just as our parents tried to educate us about cigarettes and alcohol, so we are trying to educate our children about cigarettes, alcohol, and drugs.

As our parents taught us, so some of us are teaching our children, reaching to the lessons of the past for guidance. I remember sipping wine at the dinner table to learn how and what to drink, I remember the evening of my 18th birthday, having my first legal cigarette at home, sitting on the edge of the living room sofa, smoking with one hand and drinking my first bourbon and water with the other, feeling awkward, certain that I would spill the drink or the ashes, but feeling enormously relieved that I didn't have to sneak cigarettes any more. The parental rules back then were simple and applied equally to son and daughters: you may not smoke at home until you are 18 and you will learn to drink from your parents at home, not from your friends at parties. In those days, parents living in Northern Virginia didn't have to teach their children about drugs. There weren't any around.

Sixteen years have passed since that evening. Sixteen extraordinary, unsettling years, in which a generation that had all the answers has matured into parents and now has all the troubling questions our parents had, and many more. We have more information around us about how to raise children and we probably know less. The jury's still out, but an argument can be sustained that by any past prevailing standards we are doing a worse job of raising the next generation than our predecessors, who at least insisted on a world in which their children had to learn to read and didn't have to learn about dope. At least, not when they were 12.

I didn't find out about marijuana until I went to college in New York City. Then, the only drugs used widely by young people were marijuana and hashish. LSD was still legal and was being used in lab experiments at Harvard. I didn't know how to use marijuana and met it the first time one evening after I'd spent some time with Chablis. The result left such an unpleasant memory that I vowed my children would never be so ill-informed, and, I hoped, so wretchedly sick.

A year or two ago, there was a spate of stories in the newspapers about contaminated drugs, including marijuana that had been sprinkled with PCP, being sold to unsuspecting teen-agers and doing dreadful things to them. About this same time, my son asked his first tentative questions about marijuana, much the way we asked years ago about beer and cigarettes: How do you smoke it? What does it do? Does it make you sick? For how long?

We answered our son's questions as frankly as we knew how, describing how you use it, its merits and demerits, sharing experiences, labeling the old wives' tales for what they are, but nevertheless urging him to be cautions. Further, we offered the learn-to-drink at home approach: if and when he decides to try marijuana, do so at home. Thinking of the contaminated marijuana, we said - rather presumptnously - "we'll find it for you."

I am, you see, in the new generation of enlightened parents. We know about drugs the way our parents knew about alcohol. We tell our children the truth about dope, strip it of its forbidden fruit mystique, get them involved in hobbies, sports, school projects, occupy their time, make sure they don't get in with the wrong crowd, and hope for the best.

Less than a month after my son asked about PCP, I read in the morning paper the story of Scott Peterson, 17, of Olney. The picture on the front page shows a good looking youth, proudly displaying a fishing catch. Peterson, according to his friends, loved life, loved hunting and fishing, had many friends. On July 15 after a fight with his parents over missing money, he was grounded and later that afternoon he pointed his hunting rifle into his stomach and pulled the trigger. From evidence around the house, his parents now believe he may have consumed up to 13 tabs of LSD before killing himself. By all accounts, Peterson fooled around with marijuana, but his friends say they don't think he used acid.

Peterson emerges from the news story as a frighteningly typical teen-ager, living in a family that obviously cares about him, but that has strinkingly familiar generational tensions. Peterson did not like doing chores around the house Saturday mornings. "He'd walk around with a big puss on his face," said his father, Deloyce Peterson, echoing words heard around the Beltway Saturday mornings.

Like other parents, Peterson said he often talked to his son about drugs after reading newspaper articles about their effects or after finding a marijuana pipe in his son's car. "I probably overextended myself with getting on [Scott] about marijuana," Peterson told a reporter.

As usual, no ones knows why Scott Peterson killed himself, and his friends say they are tired of adults blaming everything on drugs. A priest who knows that crowd theorizes that teen-agers now have too much, too soon, too easily, and have no sense of accomplishment. He predicts more adolescent suicides. An accompanying article charts a rate of suicides among 15 to 24 year olds that has tripled in the last 20 years, with the curve rising sharply after 1965. Some 5,000 young people are killing themselves every year.

No one here is arguing that drugs are solely to blame for what happened to Scott Peterson but it seems clear that they played a significant role in his life and how he ended it. His father may have talked too much about the dangers of drugs. I may not be talking enough about them.

Older parents may be too conservative and old-fashioned in lecturing to their children about drugs. Younger parents in my generation may be too liberal, too enlightened. We don't know and that's the point: the generation that had all the answers, that expanded its mind with LSD and paved the way for PCP and the other lethal drugs abounding now, doesn't know how to keep its children from destroying themselves.

Once again, we are experimenting.