"Rachel," a slender, blond 17-year-old, is the opposite of the stereotype of the withdrawn, surly, drug-fogged teen-ager.

She is beautiful, an "A" student, popular, helpful to her mother around the house.

She talks enthusiastically about the job she had last summer as a cook on rugged camping expeditions in the Rocky Mountains.

But Rachel has also "dropped acid" (LSD), eaten hallucinogenic mushrooms and "free-based" (smoked) cocaine. She has suffered blackouts lasting hours after mixing drugs and alcohol, and says she'd like to try heroin.

Heroin is a pain-killer, and Rachel's pain is one that seems to afflict millions of middle-class teen-agers: boredom.

"I never even wanted a 'joint' while I was up in the mountains," she says. "I just felt good. But down here there's nothing to do, so you get high. What else are you supposed to do? "

Restless and hungering for challenging experiences, she confided that she would start college mainly to please her mother.

Bored? How could they possibly be bored, this new generation of young people, surrounded as they are with opportunity and affluence and ingenious forms of entertainment? It is easy for adults to feel exasperated by the complaint of boredom, but in scores of interviews across America it became an overwhelming theme, too widespread to be dismissed merely as the whining of "spoiled teen-agers."

In Whitesburg, Ky., a town deep in the coal country of Appalachia, the "bridge crew" sits on the rail of the town bridge for hours and hours.

Most members of the "bridge crew" are in their early 20s and, a friend says, "they are not doing much except going to town and sitting on the bridge . . . .They're married, they don't have kids, they don't have a job--and they sit on the bridge."

In Des Moines, hundreds of teen-agers with nothing else to do in the evening drive their cars up and down the empty streets. They drag-race, drink beer and yell at pedestrians, a contemporary reenactment of "American Graffiti." It's called "scooping the loop," a pastime that could only exist in a wealthy, affluent country.

"I'm addicted to TV," says a teen-ager. "I can watch it from 8 in the morning to 11 at night. I can come home from school, sit down in front of the TV and watch until I fall asleep."

Adolescents are not naturally bored. They are brimming with energy, anxious to experiment, curious about the world around them. This is a time in their lives when they are learning about their bodies, experimenting with sex, trying to understand themselves, struggling to work out their relationships with friends, families and lovers.

And their boredom seems connected to this irony: children who have been given so much, many of them at least, have been denied what their parents experienced -- meaningful struggle, work which gives a sense of purpose, even sacrifice, which makes one feel needed by others.

Schools, parents and communities often take the narrowest of views about their adolescents. They sort and judge young people according to "achievement," which they define narrowly in terms of grades, college acceptances, credentials, test scores and talent. But in other important ways little is asked or expected of them.

They are deprived of responsibilities and cut off from real-life activities that are important to the adult community. They are waiting -- waiting to be grown-up. And they are bored.

"We're not dealing with the animal as God created it," says Bob Alexander, director of the experimental Living Stage in Washington. "We're trying to force kids into different molds and they're biologically rebelling and going crazy. I think by the time an average 15-year-old grows up in western society, we have driven him half-crazy."

American kids have probably always grumbled about boring schools and parents who won't take them seriously. It is a natural complaint of those transitional years, ever thus, one could say. But, for whatever reason, the disturbing evidence suggests that many young people are increasingly losing a sense of connection between what they are asked to do and what they feel they need to do to prepare for life.

When the Carnegie Council on Higher Education surveyed school principals for its 1979 study, "Giving Youth a Better Chance," it found that 41 percent of them considered student apathy to be "serious" or "very serious," putting it ahead of absenteeism as a leading school problem.

A University of Michigan study of male high school seniors found an unsettling trend: the number who think what they learn in school is "very important" or "quite important" declined from 70 percent in 1969 to 50 percent in 1980.

When Jane Norman and Myron Harris surveyed 160,000 teen-agers for their book, "The Private Life of the American Teen-Ager," they found only 42 percent who described school as "necessary" and only 21 percent who found it interesting. Twenty-seven percent said school is "boring." Another survey by the National Center for Educational Statistics found that more than half of all high-school seniors find their part-time jobs more enjoyable than their school work.

Even more startling and disturbing than the apathy of the white and privileged young is the continued alienation of the black and Hispanic underprivileged. Four out of five Puerto Rican children drop out of school in New York City.

At the Great Brook Valley Public Housing project in Worcester, Mass., neighborhood worker Carmen Ventura says Hispanic kids drop out in droves "because they're bored -- there's nothing there for them." Local officials estimate that 11 out of 12 Hispanic teen-agers who enter Worcester high schools do not stay through to graduation.

Yet businessmen in the Worcester area, foreseeing a shortage of young, skilled workers in the middle of the 1980s, are so concerned that they have formed a "career education consortium" to try to keep teen-agers in school.

The reasons for all this are enormously complicated, but they are rooted at least in part in the changes that have occurred since World War II in the conditions in which young people grow up.

Teen-agers have always lived an existence somewhat apart from adults. But until the early 1960s, American youth's separate identity in the culture seemed less distinct.

There were hints of the youth protest and rebellion soon to come in the underground culture of "The Beats," in the hip swivels of Elvis Presley and in the laconic rebels portrayed by actor James Dean. But young people grew up mainly as junior adults preparing for adult roles, and they shared many of the values and goals of their teachers and parents: the work ethic, the drive to attain status, a willingness to make personal sacrifices for the family, and the goal of material well-being.

The 1960s and '70s saw the rise of a powerful youth culture with a strong identity of its own--its own distinct music, markets, values and, for a few years, politics. Television and media broke the monopoly that schools and parents had on the information that children received. The sexual revolution extended down from parents to kids. A drug scene which was separate from the experience of adults became institutionalized, and the children of the new middle class rebelled against the values of their parents and their schools.

Out of this came a far more open and tolerant society than existed in the '50s. Many new kinds of family arrangements were tolerated, although the traditional ones remained dominant. And young people found themselves growing up in a world of expanded options and opportunities.

But the shifts left teen-agers growing up in the 1980s in a curious limbo. In some respects they live an existence that is far more "adult" than their parents did as teen-agers. There is the view, expressed by a girl, that "kids feel they have to hurry up with life."

But, at the same time, "youth" can seem interminable to young people who now mature earlier, engage in more adult activities--but must stay in school longer because of the requirements of the economy.

Through the selective eye of television and the media they know far more about world events and about the way different kinds of people deal with each other than did their parents, whose sources of outside information as teen-agers was much more limited to family, church and school.

Teen-agers are more on their own. Busy parents and busy children have radically altered the pattern of everyday family life and relationships. The family evening meal at which adults and teen-agers sat down together is no longer the norm. And some parents give their children money to eat by themselves in local restaurants.

Teen-age independence has also been strengthened by the widespread availability of low paying, unskilled jobs in fast food chains, restaurants and retail stores, which has put more money than ever before in the pockets of young people living at home.

But this impression of an increasingly "adult" youth can be misleading. For the changes have spawned a youth culture which is also surprisingly isolated from the adult society, where the influence of adults has been diminishing and the influence of teen-agers on each other increases.

A 17-year-old girl surprises her father during a frank discussion about drugs when she assures him she does not smoke marijuana regularly but "loves gin." Drugs are now part of the teen-age rite of passage, just as alcohol once was, and still is.

"Overall, drug use among high school students remains widespread," the National Institute on Drug Abuse reported in 1980. Although there has been a slight decline in habitual marijuana use among teen-agers, teen-agers are using more stimulants, such as cocaine, and hallucinogens, such as LSD, than they were in 1975.

Paradoxically, the increasing amount of part-time work by teen-agers seems in some ways to be a factor in the inward turn of the youth culture. Among older people with memories of the Depression the image of working teen-agers conjures up visions of struggling, earnest young people helping their families or saving for a college education. Some 30 percent of high school seniors earn $200 a month or more, according to the University of Michigan poll. The proportion of working teen-agers has been rising steadily in the last five years.

But indications are that much of the money goes for "discretionary" purposes: stereos, clothes, entertainment and other things that tend to strengthen the bonds to an isolated youth culture.

There is even evidence of a "drugs-for-work" connection. In the University of Michigan survey of high school seniors, the frequency of drug and alcohol use was seen to increase as earnings from work increased. Only 20 percent of students reporting low weekly income said they had used marijuana in the last 30 days. But the figure reached almost 40 percent for those who reported high weekly income. A similar connection was noted between work and alcohol use.

Along with boredom and isolation comes a sense of "oppression" that seems absurd to many adults but feels real to the kids.

New York City social scientist Ralph W. Larkin, whose book "Suburban Youth in Cultural Crisis" deals with student life in an affluent high school 30 miles from New York City, writes that "most of the students view school as inherently coercive," and even as "unpaid labor." Some refer to it as "prison."

Larkin was initially shocked at hearing privileged kids use the prison analogy, but he concluded that it was an authentic expression of their feelings:

"They are imprisoned by the lack of alternatives to what they are doing. What else could they be doing? Life in the street is mean and brutal. Full-time decent jobs for high school dropouts are extremely rare. The students are the recipients of a social policy of containment. They are being 'contained' in schools until such time as they can assume adult roles."

Larkin's analysis stirred controversy among social scientists. But a number of teen-agers, interviewed at random, agreed with the "containment" thesis.

What's going on here? A wealthy and dynamic country gives young people extraordinary benefits and opportunities and the children respond by feeling bored or, worse still, oppressed. The bewilderment of parents was summarized by a black father who himself struggled out of a background of rural poverty to reach the suburban middle class. He couldn't understand his own son's lack of motivation at school.

But a friend offered an intriguing answer:

"Perhaps he has not had your advantages."

In other words, is it possible that the very struggle of overcoming disadvantages, the work and discipline and sense of goals, is what's missing for so many of today's young people? A growing list of experts think so.

"In our efforts to be good to our kids we've done them a disservice," says B.T. Collins, former director of the California Conservation Corps, which uses 18- to 23-year-olds to fight fires and floods and perform community services. "We've failed to make them responsible for what they do or fail to do. We've failed to get across to them the joy of doing something well. We've made promises to them without exacting responsibility from them."

In survey after survey of youth, young people themselves express deep concern about their own apathy and drift.

A private committee that made a national study of the pros and cons of a system of civilian service concluded in 1979 that "little is asked of young people except that they be consumers of goods and services. . . . A vast industry serves youth with schooling, entertainment, and goods of all kinds, but there are limited opportunities for the young themselves to produce goods and serve others."

In 1977, for example, 250,000 people between 14 and 18 looking for some opportunity to serve applied for 40,000 positions in the Young Adult Conservation Corps.

Opportunities for service and experience other than the traditional ones of school and work are far more limited than many people realize. The Peace Corps, Vista, Action, the National Teacher Corps, the National Health Service Corps and the University Year of Action combined enroll fewer than 40,000 people under 24 each year.

But this is not evidence that young people are uninterested. The applicants far exceed the positions available in both federal and local community service programs.

When George Gallup polled 18- to 29-year-olds in the "barometer county" of Dayton, Ohio, he came up with what he regarded as an "incredible" finding: one out of three would like to go into the social services as a life's career.

On the basis of a nationwide youth survey in 1979, George Gallup Jr. concluded that "the youth population has been misnamed the self-centered generation. There's a strong desire to serve others. The problem we face in America today is not a lack of willingness to serve or to help others, but to find the appropriate outlet for this."

When the University of Minnesota asked 400 young people representing a cross-section of the state's teen-agers to list social problems they felt they could work on, they listed problems of the elderly, shoplifting, cleaning up lakes, painting homes of the poor, cleaning up the community, registering voters and fixing up abandoned buildings.

A young black at the Job Corps camp in Morganfield, Ky., donated blood and explained afterward:

"This is my chance to go ahead and help somebody . . . . From now on, I'm going to give every chance I can. I'm ready to help other people. I'm tired of just looking after myself."

The California Conservation Corps provides an uncompromising alternative to young people between 16 and 23 who are bored, just drifting or in need of relief from the pressures of drugs, parents, teachers.

It makes a mystique of hardship and service. A hand-lettered sign on the headquarters building in Sacramento reads: "Try Us--You'll Hate Us!" The corps motto is "Hard Work, Low Pay and Miserable Conditions."

Two out of three drop out before completing the full 11-month tour of duty--though a substantial number of the dropouts return to finish later. And it has a waiting list almost as long as its enrollment of 1,840.

At an annual cost of $18,000 a person, the corps is hardly a model that can be widely copied though former director B.T. Collins says it more than gets its money back in lives saved, forest fires extinguished and property protected and improved.

But Collins and Gov. Edmund G. (Jerry) Brown Jr., who initiated the idea, claim its philosophy of discipline, responsibility, accountability and service is what is needed to inspire youth, and could be duplicated by schools and communities across the country.

Corpsmen live in austere, often remote campsites and have to follow the rules laid down by the tough talking, hard-swearing Collins: no alcohol, no drugs, no violence, no destruction of state property, no refusal to work--or "hit the highway."

Gillian McCallum, 19, is a soft-spoken girl who lives near San Francisco. A year and a half ago she was living a comfortable life attending Diablo Valley College. But then she chucked it for "low pay and miserable conditions."

"My father came to the dorms and asked one question: 'Why?' He didn't understand. I told him I wanted a break and that I was tired of people saying we were the 'Me' generation. In the end he understood. Now he's backing me completely."

On the day I visited a campsite 30 miles up into the hills near Sacramento, Michelle Priestly, 22, a long-haired, pale young woman from Marin County, had just arrived. She had signed up on the recommendation of her boyfriend, a CCC veteran, to "get away from drugs, the street scene and the alcoholics."

In the dining hall another young woman from Marin County told her story:

At 15, she had moved away from the home of her divorced mother because she didn't like her new father-in-law. She moved in with her boyfriend, a drug dealer. By early 1981, she was in deep trouble. She had become a heavy user of Persian heroin and was smoking ("free-basing") cocaine. She was malnourished, emaciated and scared. One night when her boyfriend was away, two of his customers robbed her at gunpoint. Since then she had been afraid to leave the house alone.

Finally, she had gotten up her courage and joined the CCC "for the discipline."

The new routine had not been easy for her. A few weeks earlier she had been caught in the men's dormitory and suspended for a week without pay, along with the man she was visiting.

They holed up in a motel and considered what to do. She returned to camp--alone--for one more try.

She acknowledges that she has her "moods," and still has trouble handling authority. And she still battles a craving for drugs and loneliness for her old boyfriend. But, she says, she's determined to stick it out.

The boredom of youth, and the success of programs such as the California Conservation Corps, are behind a little-noticed debate over possible alternatives to the traditional route from kindergarten to the workplace.

Many of these efforts center on getting young people out of the classroom and into the community or the workplace, either to learn skills or to help in providing badly needed community services.

Two examples of existing programs of this kind indicate what already is being done.

In New York City, some large banks have been making computer time available to public school students for several hours a week.

A program at Baltimore's Northwestern High School, which was set up with the help of federal funds and backed by the state board of education, works on the premise that service is a part of education. Hundreds of students give up one day a week of classes to work at hospitals, banks and elementary schools.

Would street-wise city kids in need of money and high school credits sign up for volunteer for which they got no pay or academic credits? At Northwestern the answer was yes.

For some kids the military is an option, but as Northwestern University sociologist George C. Moskos has reported, today's U.S. military All-Volunteer Force has virtually written off attempts to recruit white, middle-class kids.

A mere 5 percent of today's enlisted men have had some college experience, down sharply from the pre-Vietnam period of conscription when 13.9 percent of the enlistees and 17.2 percent of the draftees had some college background.

Concern over the adequacy of the All-Volunteer Force in recruiting manpower for the military has spurred renewed discussion of some kind of system that would give young people an option of civilian or military service.

The main concern driving this discussion is the expected decline in the pool of 18-year-olds available for service in the 1980s--from 4.2 million now to an estimated 3.4 million in 1990.

When asked about national service, 18- to 24-year-olds surveyed nationally by Gallup were 77 percent in favor of a voluntary program, and 42 percent were for a compulsory one for men. On the basis of the poll, Gallup estimated that 4 million of the 29 million people in this age group were "definitely" interested in serving in either a military or non-military capacity, and an additional 6 million "might be interested."

That would be a significant change from the way young people come of age now, in a sense, a restoration of values and experiences that many of their parents knew when they were growing up.

"Without the hope of work that serves the healthy development of self and society, adolescent values curdle into cynicism and the young escape into speedy gratification through fantasy and drugs," writes psychologist and author Michael Maccoby in a new book, "The Leader."

"Without ideals and a sense of participating in something of value to their society, they will embrace egoistic ideologies.