The United States seems to have left school desegregation behind.

Not that the job has been completed. Most black students attend majority-black schools.

Not that anyone is proposing that black and white students be separated by law, as they were in 17 states before the U.S. Supreme Court ruled, 40 years ago this week, that "in the field of public education, the doctrine of 'separate but equal' has no place."

But political and demographic trends are combining to limit how much children of different races are brought together. Even the goal of having black and white kids in the same classrooms is being questioned, while a new generation of race-related issues -- performance gaps, tracking, Afrocentric curriculum -- is getting more attention in the post-desegregation era.

Nationally and in Maryland, there was dramatic change in the 20 years after the 1954 decision in Brown vs. the Board of Education of Topeka, Kan. Some school districts -- including Baltimore and suburban districts in Maryland -- moved almost immediately to dismantle their legally required separate school systems. Other districts -- in Southern Maryland and the Eastern Shore, and throughout the South -- moved much more slowly, but eventually were pushed into action by federal pressure and court orders.

At first, desegregation seemed simply a matter of allowing blacks to attend previously all-white schools. Then, the legal ground shifted, leading to desegregation plans including the often-reviled "busing" -- moving students so that one school in a district looked pretty much like another in terms of racial composition.

But while there was dramatic change in the first 20 years, national studies show that over the ensuing 20 years there has been little change in the amount of racial isolation in schools. There has even been some resegregation in the past decade.

Governments are no longer pushing much to change this trend. Neither are most civil rights organizations, which tend to talk more these days about providing opportunities for all students and less about making sure that black and white children are attending the same schools.

And while political pressure has lessened, changes in housing patterns have made desegregation problematic. Whites moved out of central cities (in many cases, the movement began before 1954). For a while, people talked about a "doughnut" problem -- a ring of white suburbs surrounding a black city.

Now, the doughnut is disappearing. Blacks and other minorities also began to move to the suburbs. But often the result was not integrated suburban neighborhoods but minority concentrations in new locations.

Here's how those trends have played out nationally and in Maryland:

Urban school districts have been left with school-age populations that are overwhelmingly African-American and Hispanic. A December report of the Harvard Project on School Desegregation found that, "In the central cities, 15 of every 16 African-American and Latino students are in schools where most of the students are nonwhite."

The 25 largest urban school systems, the report said, contain 30 percent of all Hispanic students, 27 percent of all black students and 3 percent of all white students.

In Baltimore, while black population remained virtually unchanged between the 1980 and 1990 censuses, white population dropped by about one-sixth. In the current school year, fewer than 16 percent of the public school students are white. Of the city's 178 schools, 114 have minority enrollments of 90 percent or more.

Desegregation once seemed a problem only in large cities or in the South. But as minorities moved to the suburbs, so did desegregation issues.

Some suburban school districts have desegregation plans, but school enrollment patterns in most suburbs match housing segregation. The Harvard study found that in suburbs of the 33 U.S. cities with populations over 400,000, 58 percent of blacks attend "majority minority" schools and 22 percent attend schools where the enrollment is 90 percent or more minority.

Although many suburbs treat minority populations "like an infectious disease," says Gary Orfield, director of the Harvard Project on School Desegregation, "Suburban communities need to realize they are going to be much more diverse a generation from now.

"Suburbs will not be immune to the problems of the cities unless they do something different than the cities," Dr. Orfield says. "There ought to be suburban housing and school desegregation policies. People should discuss very seriously whether they want to relive the center city experience."

While few suburbs have "busing" programs for desegregation, some are attempting to improve racial balance by open enrollment programs -- allowing parents to choose the schools their children will attend -- or by magnet schools designed to attract children from outside a neighborhood.

In Maryland, the number of "majority minority" schools in the suburbs (more than 50 percent of students black, Asian, Hispanic or Native American) has grown from 154 to 259 in just the past five years.

Much of the growth has been in Prince George's County, where African-Americans are now 69 percent of school enrollment. Outside Prince George's, the number of "majority minority" schools in Maryland suburbs has grown from 49 to 87.

Included in those "majority minority" schools in the suburbs (and outside Prince George's) are 12 in Baltimore County, eight in Montgomery County and three in Anne Arundel County, where more than 75 percent of the students are minorities.

A school with an enrollment that is, say, 60 percent black and 40 percent white might not seem like a problem. But the track record shows that many whites are uncomfortable when they are in the minority, so such schools -- and their neighborhoods -- are likely to become more segregated over time.

To the extent that there has been public debate over these patterns, however, it has largely focused not on enrollment but on resources and achievement.

Stuart Berger, school superintendent in Baltimore County, who has just begun a magnet school program to improve racial balance, said he was under no pressure to balance enrollments, although "from the African-American community, we were hearing that they were not satisfied with our expectations for their children."

He says he began a voluntary desegregation program because "I was just concerned that housing patterns had caused some schools that were 90 percent African-American and some schools that were 99 percent white. Given the diversity in our society, that didn't seem like a healthy situation."

Black groups, however, say the goal is not racial balance but equity.

"The objective always was access to more resources and better educational opportunities," says Margaret Simms, director of research programs at the Joint Center for Political and Economic Studies, a Washington think tank that studies African-American issues.

Alvin Thornton, a professor of political science at Howard University and chairman of the Board of Education in Prince George's County, agrees. The emphasis on "moving students around," he says, "is losing steam with both black advocates and white advocates."

"When the gap between black and white students [on achievement and college entrance tests] is erased, when they are going to the same colleges at the same rates, then no one's going to give a damn about desegregation," Dr. Thornton says.

Attention to educational opportunity rather than pupil assignment has produced a new generation of race-related issues:

* "Catch-up" efforts for minority schools.

Some districts, including Prince George's County, provide extra money for schools with high minority concentrations.

So far, the Harvard research group found, these programs have not been successful in lifting these schools to the achievement level of others. "It's very difficult" for such programs to succeed "in a school system without adequate funding to begin with," says Dr. Thornton. Yet systems with such schools are often fiscally strapped.

* Access.

In many more districts, there has been debate over what happens within schools and within classrooms: How many African-American students are in gifted classes? How many are in special education classes? How many get suspended? How many take college-preparatory courses such as physics and geometry?

Dr. Berger has made it easier to get into gifted classes in Baltimore County. Critics say that he is lowering standards and watering down course content. He says that he is giving more children a chance, that he expects the percentage of black students in gifted classes to double, "and we have no indication that they're not doing well."

* Minority-centered programs.

Another controversial topic has been whether African-American students are best served by programs designed especially for them.

Some large cities, including Baltimore, are experimenting with versions of "Afrocentric" curriculum. The theory is that concentrating on African history and culture will lead black students to perform better.

Others believe that black students have different "learning styles" to which schools should adapt. Some systems even have special schools for black males, who tend to do poorly relative to whites or to black females.

* Linguistic minorities.

Increasing populations of Hispanic and Asian students are creating new sets of issues. Far from the old desegregation approaches, advocates often want these groups concentrated where they can receive bilingual instruction and other special programs.

In Maryland, these "new minorities" represent a relatively small HTC portion of students -- Asian-Americans are 3.7 percent of enrollment and Hispanics are 2.9 percent. But the numbers are growing. Between 1980 and 1990, this was the percentage growth in population in Maryland: whites, 7 percent; blacks, 24 percent; Hispanics, 93 percent; Asians, 117 percent.

Advocates of desegregation believe that racial and socio-economic balance contribute to learning, especially since schools with high minority concentrations are often schools where most of the students come from low-income families.

"People mix up the effect of race and poverty," says Dr. Orfield, the Harvard desegregation researcher. "There's no effect [on achievement] just sitting next to a white kid, but there is a significant effect from going to a good middle-class school."

Others maintain that desegregation is important because different groups need to get to know each other.

"As I talk to PTAs, even in mostly white schools, I find that most parents buy the idea that their children are going to live in a multicultural world, and they want the school system to prepare them," Dr. Berger says. "But they don't want their children to have to travel a long distance to get to school or go to a place they perceive as unsafe."

Desegregation "isn't just about test scores, it's about getting along," says James McPartland, director of the Center for the Study of the Social Organization of Schools at the Johns Hopkins University. "You can't practice by watching 'The Cosby Show.' "

I= M. William Salganik is editor of the Perspective section.