A peek at the future through the attitudes of the young

''A simple hairline scratch.'' That's all that remains of ''the generation gap'' - the rift over ethical, social, and political values that characterized so many parent-child relationships in the 1960s and '70s.

Or so say today's youth. America's young people generally get along well with their parents, have great respect for them, and share many of their values. ''Not trusting anyone over 30,'' writes Janis Cromer, ''is a sentiment from a bygone era.''

Ms. Cromer is the author of ''The Mood of American Youth,'' a 64-page study based on a 1983 nationwide poll of students in Grades 7 through 12. Released last month by the widely respected National Association of Secondary School Principals, it received a flurry of attention that was wider than it was deep.

It deserves much more - not only for its stout affirmation of family harmony, but also because it is one of the most fascinating documents of our poll-struck and future-oriented age. Most major surveys, dealing only in adult opinion, tell us where we are today. But a thoughtful and comprehensive study of soon-to-be adults (which this one is) tells us about tomorrow. It measures, in a way, the nation's velocity and direction - just the data from which a canny cartographer of social trends can draw a map of tomorrow's world.

It's a world far less surprising than some adults might have feared. Not only is the home front (one of five major areas covered in the poll) a ''relatively quiet setting'' for most students. In other areas, too, the survey gives credence to the nation's widely noted drift toward more traditional values:

* Schools. Most students like their schools, their principals, and their teachers - although they do less than four hours of homework a week and list ''friends'' and ''sports'' above ''learning'' as reasons for liking school. In overwhelming numbers, they think math and English are the most important subjects to study (although they don't necessarily like them). And, sensing the nation's drift toward more global communications, they list computer science and foreign language among the subjects missing from the curriculum that are most needed.

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* After-school hours. Today's young people spend about six hours a day watching television or listening to the radio, but they also say they read two books on their own each month and begin a third. Some 92 percent of them think high school students should have part-time jobs; 4 in 5 regularly watch or listen to football games; and over a third of them are active in religious groups.

* Politics and values. Breaking with traditional conservative or liberal designations, today's students mix attitudes of both. Supporting capital punishment and opposing the legalization of marijuana, they also want handgun control. Asked to list the worst influences on young people, they began with drugs and alcohol - and then, with candid self-discernment, added peer pressure and television. The most important national problem: unemployment. The most important global problems: the threat of nuclear disaster and a World War III.

* Future plans. Most students, satisfied with their own upbringing, plan to raise their own children as they were raised. And they do plan to have children - on average 2.4 per family. Despite all the talk of the swinging singles life, only 5 percent intend to remain childless. Ranking their goals, they list (in order) career success, happiness, and marriage and family.

As with any poll, some caveats are in order. Students, like adults, can be shockingly traditional and timid. As anyone can report who has administered teacher evaluations (as I have), they can be terribly kind toward and forgiving of their superiors - saying nice things even when the class was pretty awful. Like adults, too, they are capable of responding to survey questions by saying what they think ought to be said. So some of the findings here - about the numbers of books they read, for example, or the quality of teaching in their schools - have already caused raised eyebrows among teachers, administrators, and parents.

Yet even wishful answers, reflecting some of the idealism of youth, paint an instructive picture. They tell us what today's youth want their world to look like. And, in marked contrast to stereotypes of the young as flaky idlers or radical dissenters, they feel strongly (writes Ms. Cromer) that ''most adults have worked very hard to achieve their own goals.'' Some 96 percent of them say they, too, plan to work hard for their goals.

All of which, of course, raises some profound questions. Has our present crop of adults done a good enough job resolving world problems that we want the next crop to emulate us? Or do we need more healthy skepticism?Are we bringing up a future in lock step with the present, or are there new ideas bubbling under the surface?

The Student's Viewpoint Cited as nation's problemsm % All 1. Unemployment 52.0 2. Inflation 21.1 3. Crime 20.8 4. Poverty 6.4 5. Health and welfare 5.5 6. Energy 4.9 7. Social Security 3.9 8. Sex Discrimination 3.1 9. Ecology 2.9 10. Racial tension 2.6

The Student's Viewpoint What I want out of life % All 1. Career success 27.6 2. Happiness 25.7 3. Marriage/family 20.8 4. General success 9.8 5. Financial success 7.0 6. Long/enjoyable life 4.2 7. Education 3.2 8. Religious satisfaction 3.2 9. Friends 3.1 10. Personal success 3.1

The Student's Viewpoint My yearly spending Male Female 1. Savings $145 $130 2. Clothing 57 143 3. Entertainment 95 55 4.Transportation 79 96 5. Food 60 63 6. Travel/vacations 31 39 7. Education related 17 43 8. Insurance 22 34 9. Personal Care Products 7 41 10. All others 15 30

The Student's Viewpoint After high school % All % Male % Female 1. Four-year college 54.5 41.0 57.6 2. Get a job 36.6 33.4 39.3 3. Junior college 14.8 12.0 17.1 4. Training/vocational school 14.8 16.3 13.5 5. Get married 13.3 8.9 17.1 6. Join armed forces 11.1 18.5 4.6 7. Travel 9.4 6.7 11.8 8. Join volunteer organization .9 1.6 .4

The Student's Viewpoint Reasons for liking school % All % Male % Female 1.Friends 71.9 71.0 72.6 2. Sports 31.2 37.0 26.2 3. Learning 17.1 16.0 18.1 4. Social Activities 16.0 9.1 22.0 5. Teachers 15.1 13.8 16.2 6. Classes 10.2 8.9 11.4 7. Cocurricular activities 7.3 8.2 6.6 8. Other things 9.7 12.0 7.7