The black children of the civil rights era have grown up and they are different from their parents' generation -- more engaged in the white world, yet also more suspicious of white people's feelings about them.

Now adults in their twenties and thirties, these young blacks are more likely to have gone to college, more likely to be living and working among whites than their parents. But notwithstanding this greater familiarity, these young black adults express greater mistrust of whites, a Washington Post-ABC News national survey of racial attitudes reveals.

Many of the age differences in black opinion are differences in degree. Both young and old share a general belief that blacks have made substantial progress over the last decade, but they also express apprehension that the rightward turn in the public opinion of white America presages a new era of setbacks for blacks.

Among upwardly mobile black adults under 40, the feeling that white racism still cripples black progress is stronger. They believe, more deeply than their elders, that violent protest has been the effective prod that forces government to act on the problems of blacks. A majority of college-educated blacks believed violent protest can be justified -- an attitude not shared by a majority of any other group, white or black.

The oldest of the members of this generation were teen-agers, still in junior high, when the Supreme Court ordered an end to school segregation in 1954, the degree that launched an era of change, riot and protest and political and economic strides for blacks. The youngest of today's black adults were not yet born then and the system of legally imposed segregation is only history to them -- for many of them, hazy history.

Eleanor Holmes Norton, chairman of the Equal Employment Opportunity Commission in the Carter administration, calls the entire group the "crossover generation." They are the ones who rode the school bus and integrated colleges, continuing their education after high school in 2 1/2 times the numbers of their parents' generation.

On college campuses, they wore dashikis, grew their hair in long bushes and raised clenched fists as they shouted "Black Power." Now, the Afros clipped and styled, the dashikis packed away in favor of suits and dresses, these young blacks are breaking into the professions and suburbia.

But, meanwhile, they cling to a deep suspicion that large numbers of whites secretly share the same attitudes towards blacks as the Ku Klux Klan, Under 40, for instance, nearly three-quarters of black adults believe that the klan represents much more than a small splinter group among whites. Among blacks over 40, however, fewer than 40 percent feel that way.

In further contrast, college-educated blacks see more discrimination in the struggle for advancement than do blacks with less education.For instance, blacks with a high school diploma or less believe, by almost 2 to 1, that "if blacks would try harder, they could be just as well off as whites." Blacks with at least some college degree with that -- by almost 2 to 1.

And yet these well-educated young blacks are clearly less fearful of plunging into the white world than their elders. For instance, a majority of the college-educated young blacks are not afraid of sending their children to an all-white school. Indeed, they regard that fear as an expression of racial prejudice. Older and less educated blacks regard it as common sense.

That does mean, however, that ambitious young blacks trust the white institutions they are encountering.

Question: are blacks discriminated against in seeking jobs as managers? College-educated blacks overwhelmingly believe they are -- 81 percent answer yes. Other blacks are less certain -- 53 percent of them say yes.

Whether this sharp suspicion of whites among young black adults is a vestige of old attitudes formed in the days of stormy campus protest or is based more on personal experiences at the moving racial frontier could not be measured by the poll. The Post-ABC poll interviewed 1,872 adults, including 446 blacks, from Feb. 26 to March 5.

What is clear is that many of the members of this "crossover generation" are pushing at barriers where resistance is still strong. The travail of a Howard University graduate with credit cards and a good job being politely but unconvincingly told that an apartment has been rented even though the vacancy sign is hanging out front, has been elevated to song in Stevie Wonder's new hit album, Hotter Than July. Aye, you might be a great doctor You might be a great lawyer You might possess the key to the city . . . Say you might have the cash but you Can . . . not cash in that face We don't want you living in here

A 25-year-old black Vassar graduate now working in Washington grew up in the Midwest believing that race accounted for "only about 5 percent of what was important about a person." But she found out about racial hostility when she shopped for bargains last winter in a fashionable discount dress store at a suburban Virginia mall.

There she brushed up against a white woman who shouted angrily, "You stupid nigger. You probably came from the District. Why don't you go back there?"

Stunned and unbelieving, the young black woman responded, "But this is 1980."

"It may be 1980, but you're still a nigger," the white woman said.

But feelings of antagonism can cut both ways. Willie Gully, who is black and in her early thirties, works at the Western Electric plant in Shreveport, La., where many of her fellow employes, and some of her friends, are white. But Gully distinguishes between white people in general and her white friends.

"I don't have love for white people but I can go along with them up to a point. We are all prejudiced in our own way. As a person, some of them are wonderful. You don't ever know what you got until you do something with it," she said.

Norton, the former EEOC leader, said she has observed an ambition and impatience among some upwardly mobile young blacks to get to the top of their professions that sometimes causes them to see discrimination when, in fact, they are traveling at the same speed as their white counterparts.

It appears also to be true that young black adults who are pioneers in their professions are often anguished by a belief that, because of their color, they are still operating in a world where there is a ceiling on the heights they can achieve. The frustration comes from not knowing where those limits are set -- and whether they are based on race or performance.

Large numbers of black children of the civil rights era never made it that far. They and other blacks still tend to be concentrated in menial jobs, living in city slums of the industrial North or small towns of the South. They tend more to look to the government for help in improving their condition.

Nevertheless, the successful young black adults, a group generally regarded as having benefited the most from affirmative action programs, tend to disagree with the statement that the government ought to compensate for past discrimination by giving to blacks who need it help that white people in similar economic circumstances would not get.

A 35-year-old black man who owns his own landscaping firm in California and makes more than $50,000 a year, takes what is, perhaps, the extreme view on this controversial issue.

"I think the whites are discriminated [against] today," he told pollsters. "I'm not going to look backward 40 or 50 years. Everyone in every country has been dominated. I don't think government should be involved in quotas."

Bernice Scales, 32, a dentist in Augusta, Ga., does not go that far, but she believes that the last decade has been one which produced mixed results for blacks.

"I think that as a few people got into better positions, there were others who fell into the same old bad positions," she said. But she also opposes measures to give special preference to black people.

"I think it would make some people feel they deserve this because of what has happened to others and would not give them the drive to achieve, and I also think it would create animosities among whites," she said.

Gully, the Western Electric worker, favors some from of affirmative action but she, too, is concerned about the motivation of some blacks.

"We've got some of these blacks on this welfare who can get up off their tails and get a job," she says matter-of-factly.

Norton said she believed these differences in opinions are a natural response by blacks to rapidly changing racial realities in the country.

"It's incredibly confusing to be black today," Norton said. "You're black, you come from the ghetto, you get into Harvard, your brother has been in the juvenile delinquent home, twice. . . . Blacks are bound to be confused by that and whites who see these different types are also confused.

"What we are seeing is the breakdown of monolithic black opinion because we have blacks across the full array of the class spectrum," she said. "All of us used to be the same people. Now blacks come in many different varieties. This is going to increase."

There are, of course, still many issues for which blacks of all ages and classes tend to agree.

Strong feelings of apprehension about President Reagan run across the spectrum of class and age. There is a strong perception that he will do less for blacks than Jimmy Carter did, but blacks also have other problems with Reagan, including his economic strategy and his foreign policy.

They tend to view him as the rich man's president, disagree with his emphasis on cutting spending to curb inflation, believing more than whites do that costs have spiraled more because of rising energy prices than the growth of social programs. Blacks, unlike whites, feel that the proposed cuts will hurt the poor.

The murders in Atlanta and the killings of blacks elsewhere have also brought about a consensus among blacks, a consensus of alarm.

Willie Gully follows closely the news about the Atlanta murders and wonders why police have not just been able to solve them.

"Nobody can do nothing," she said. "But they can pick up all the prostitutes, all the muggers. They can do that.

"It's going to be a mess in Atlanta if these people don't come up with something," she said.

But the growing differences between young and old blacks and those who have made it and those who have not on other issues has caused some concern among civil rights activists and scholars.

"Upwardly mobile blacks ignore the real danger that their own progress could be threatened if the public mood becomes more reactionary," psychologist Kenneth Clark and American historian John Hope Franklin wrote recently. "Moreover, demagogic leaders could arise who might try to turn the resentment of the underclass against blacks who have left them behind." How the Survey Was Conducted

A total of 1,872 people nationwide were interviewed by telephone in The Washington Post-ABC News poll on attitudes toward race relations. Included were 446 blacks, the large majority of whom were selected from a special random sample of blacks to ensure adequate black representation in the poll.

Whites were interviewed by white poll-takers and, where possible, blacks were interviewed by black poll-takers to reduce the chances of inhibiting respondents. In all, 354 of the blacks, or 79 percent, were interviewed by black interviewers.

The theoretical margin of sampling error in a poll of 1,872 people is about 2.5 percent in either direction for figures derived from the entire sample. Figures based on the 446 blacks interviewed are subject to a sampling error of about 5 percent in either direction.