For the second time in 10 years, the Prince George's County school board will appear in federal court to defend itself against charges that the huge suburban school system has failed to desegregate.

The trial opens today in Baltimore before U.S. District Court Judge Frank A. Kaufman, the same judge whose desegregation order in 1972 resulted in massive busing. It revolves around complaints that the once segregated system, the 13th largest in the nation, never fully mixed its black and white pupils.

The cast of characters also is familiar. The plaintiff is the county NAACP, which says it is acting on behalf of all black residents of the county, including some who were the plaintiffs in the original suit. The defendants are the predominantly white (eight of nine members) school board, only two of whom were on the board in 1972. The board contends the NAACP doesn't represent county blacks.

But some things have changed in Prince George's County in the intervening decade. Since 1970, some 153,000 white residents were replaced by 156,000 blacks--one result of busing for integration, according to some observers. This increased the black population of the county to 37 percent from 13 percent. Similarly, the public school population changed from 23 percent black in 1972 to 52 percent this year.

The NAACP lawsuit complains that:

Slightly less than half of all black students attend schools that are either less than 32 percent or more than 72 percent black.

The number of black teachers, now about one in four, has not kept pace with the growth in black population of the county, and black teachers and other professional staffers are likely to be assigned to schools with heavy black enrollment.

Black students are more likely to be disciplined than whites, and are disproportionately assigned to special education classes.

Fewer blacks than whites are assigned to the Talented and Gifted program. Blacks comprised 49 percent of the county's students in 1980, but only 12 percent of those in the special classes.

School closings ordered by the board, in the face of dwindling enrollment, exacerbated the racial imbalance.

The central question before Kaufman will be whether the schools were ever desegregated in the first place. If he agrees with the board that they were, then the NAACP will have the more difficult task of showing that the statistical inequities result from intentional actions by the board.

If the judge finds that his desegregation order was never effectively accomplished, then the county schools may face another court-ordered remedy for a grievance that dates to 1954.

The school board's position is that even if these and other conditions cited in the lawsuit constitute segregation, the NAACP must prove that the board brought it about intentionally.

The school board's attorney, Paul M. Nussbaum, complained to the court that the plaintiffs are seeking to condemn school officials and Prince George's residents "to the fate experienced by the characters in Sartre's 'No Exit' who must for eternity relive a set of events."

Brian J. Porter, the schools' information director, said the plaintiffs "have failed to go beyond the statistics and ask why. They have looked at suspension of black students, for instance, and concluded that they were disciplined because of prejudices, even though there is no such evidence of that." Porter added that "there is not a single example" that any of the school closings or teaching assignments had racial purposes.

Before the court-ordered busing plan went into effect in January 1973--over the opposition of an antibusing school board majority--126 of 218 schools were composed 90 percent or more of a single race. One month later, 203 out of 220 schools had black populations between 10 and 50 percent, the acceptable range set by the judge under the desegregation plan.

But by September 1973, 32 schools had fallen outside the guidelines. The number, adjusted for the growth in black population, has increased ever since.

This year, 87 of 194 schools are what the plaintiffs call "racially identifiable"--a term they use to mark schools that vary by at least 20 percentage points from the percentage of black students in the system. Since the county school system currently is 52 percent black, schools are "racially identifiable" if they are less than 32 percent or more than 72 percent black, the NAACP claims. The school system refuses to recognize the term "racially identifiable," Porter said.

School officials argue that trying to keep nearly 200 schools within 20 percent of total black enrollment, in a county where population is constantly shifting, is as difficult as trying to hit a moving target.

Nussbaum, the board's feisty lawyer, stresses that Judge Kaufman himself oversaw the implementation of the plan from its inception to the day he "relinquished jurisdiction" in 1974.

But the NAACP lawyers contend that the school board was well aware that the plan was failing its objectives, yet did nothing about it.

The plaintiffs cite Beltsville Elementary school, where black enrollment was below the 10 percent minimum in September of 1973. According to the NAACP complaint, school officials promised that "natural integration" would gradually desegregate the school. But the black percentage actually declined between 1974 and 1976 to as low as 8.1 percent, even as the number of blacks in the county was rising swiftly. In 1981, after mergers with other elementary schools slated for closure, Beltsville Elementary was 15 percent black.

The desegregation plan approved by Judge Kaufman on Jan. 29, 1973 intended that schools become no less than 10 percent and no more than 50 percent black in a system that was 24 percent black at the time. The plan initially contemplated that only 13 of the 228 schools would fall outside of the "10 and 50" percent guidelines. But almost immediately after the reassignments were ordered, many of the schools began to exceed the guidelines, because of growth and movement of the population. By the fourth month after Judge Kaufman's ruling, for example, the number of schools outside the guidelines had increased to 23. By September 1980, 120 of the then-216 schools were outside the original guidelines.

The NAACP says that the current percentage of racially identifiable schools--45 percent--almost equals the 48 percent situation that existed when Kaufman ruled in 1972 that the county was operating dual school systems.

Not only has the percentage of black teachers fallen behind the overall black population of the county, but according to the NAACP, the schools have "failed to root out" segregrated faculty at individual schools, resulting in the highest percentage of black teachers working at the schools with the largest black populations. Fairmont Heights, Suitland, Potomac and Central high schools, for example, where black enrollment ranges from 71 to 82 percent, also are where the most black professionals are found. Similar imbalances exist at elementary and junior high schools.

Even within schools, the NAACP charges, classes often are segregated. For example, they point to Charles Carroll Middle School, which is 58.5 percent black. Yet one seventh grade English class has 27 white and 8 black pupils, and another section of the same class has 33 blacks and four whites.

At Green Valley, the most segregated school in the county (95.5 percent black), all of the white children are in one of two fifth and sixth grade classrooms, leaving the other fifth and sixth grade sections 100 percent black.

At the other extreme, Laurel Elementary, which is only 10 percent black, has divided its black first graders so that they are placed in only two of the three sections.

Both sides in the court battle acknowledge that communication problems have brought them before a judge once more.

Board member Angelo Castelli said the seeds for this latest round were sown when board attorney Nussbaum and then school board president Norman (Chuck) Saunders negotiated a secret deal with former NAACP county president William Martin to reduce busing in February 1979.

Martin was ousted from his post in a storm of criticism from the local and national NAACP groups. The agreement, despite subsequent efforts by Saunders to get it approved by the plaintiffs in the original suit, was never implemented. Saunders also came under fire from board members who felt he did not have the power to negotiate without their approval.

In its trial brief, the NAACP contends that Saunders offered one of the original (and current) plaintiffs, school teacher John Williams, a higher paying job in the school system in exchange for his approval, and bet another plaintiff $100 that he could not get the other plaintiffs to agree to a plan to reduce busing.

"From that point on, serious dialogue stopped" between the board and the NAACP, Castelli said.

Castelli, like five of the six board members interviewed for this article, said he simply does not understand what the NAACP wants.

But the board's sole black member, Bonnie Johns, said she has been trying to impress her colleagues with "equal educational opportunity," the phrase that black leaders say is more significant than busing, for years.

"It doesn't just mean that every child has the same book. It means you provide the setting to make the education equal," said Johns, who stressed that she is not the liaison between the board and the NAACP.

Johns said to some degree, the county still operates dual school systems, a central question before the court. "You may have the absence of people calling black children 'niggers,' but you also may have the absence of an attitude that will make them succeed and provide them an equal educational opportunity," she said.

The trial is expected to last four to six weeks. The school board has budgeted $280,000 for its defense.