About 20 years after blacks started migrating to Prince George's County in large numbers and six years after court-ordered busing began, there are for the first time more black and minority students than whites in the county's public schools, enrollment figures revealed yesterday.

Since busing began in 1973, there has been a 41-percent drop in white student enrollment and a corresponding 45-percent increase in the number of black students. As a result, blacks and other minorities now make up 51.1 percent of the 127,000 public school students, and whites constitute 48.9 percent.

The figures also show that despite the busing ordered by a federal court to eliminate predominantly black schools, more schools than ever -- almost half -- are more than 50 percent black. The court-set guidelines said no school should be less than 10 percent nor more than 50 percent black.

In the predominantly white areas of Laurel and Bowie, there are three schools where black enrollment is below 10 percent.

Josie Bass, head of the Prince George's branch of the NAACP, which brought the suit that led to the busing order, said yesterday, "We are back in the situation of one-race schools" and blamed the school board for failing to continue desegregation efforts.

When U.S. District Judge Frank Kaufman issued the busing order in Janurary 1973, he was seeking to eliminate the black majorities that then existed in 46 schools. To accomplish that children were bused from what were predominantly black schools and from black neighborhoods to white schools. w

But in the six years since the plan was adopted, new black families have moved into Prince George's and altered the racial makeup of many previously white neigborhoods. The migration has changed school patterns more than the makeup of the general population in the county, which is estimated now to be somewhat more than 30 percent black.

Many white families have moved their children to private schools, further altering the racial balance in enrollments.

Since 1972, white enrollment in the public schools has fallen by 57,000 students to the current 62,195 whites still in school. During the same period, black enrollment increased by almost 20,000 students to the present 60,201. The number of other minorities has increased from about 2,500 to 4,500.

And there has been an overall decline in school enrollments from 161,969 in 1972 to 127,108 this fall.

But the original busing patterns have remained the same.

School board chairman Norman H. Saunders, an opponent of busing, said yesterday the new figures "don't surprise me a bit. The system has been moving this direction since 1973. The system is going blacker."

In the last few years, several board members have put forward plans to reduce the amount of busing in the county, citing "white flight" and the cross-busing of students from one integrated neighborhood to another. Recently, the board appointed an advisory committee to study the issue.

Many board members said the new enrollment figures demonstrate the need to update the 1973 plan.

"I have no doubt that busing has not accomplished what is set out to do," said one member, A. James Golato. "They set out to eliminate the vestiges of a segregated school system by busing, but we know now that white flight, sending kids to private schools and the upheaval of busing didn't work. More schools now are segregated."

Bonnie Johns, the board's only black voting member, said yesterday that the population shift in the county schools "follows the pattern of population changes in the entire Washington area. First there was flight (of whites) out of the District of Columbia into the suburbs, and now it is reversing itself."

"It's not busing that's the problem, because many of these people put their kids on a bus to go to private school," Johns added. "I don't think there is anything that will stop people from leaving if they don't want their kids with blacks," Johns said.

The continued climb in black enrollment reflects the growth of Prince George's black population in this decade. From 1970 to 1975, the most recent estimates available from the Maryland Center for Health Statistics, the number of blacks increased 86 percent to a total of 89,000. During the same period, the country's overall population went from 15 percent black to 28 percent black.

The figures released yesterday show that of 19 senior high schools, seven are now more than 50 percent black. Only Bowie Senior High was less than 15 percent black.

Of 41 junior high schools, 21 has black enrollments exceeding 50 percent. Only Samuel Ogle, also in Bowie, was under 15 percent. Of 145 elementary schools in the county, 73 had black populations exceeding 50 percent. Three elementary schools -- Bond Mill in Laurel, and Meadowbrook and Rockledge in Bowie -- were more than 90 percent white.

Jon Peterson, director of the schools' pupil accounting division, said the school system has stopped analyzing the yearly shifts in racial composition because "the school board saw fit not to change busing lines."

He said that to reduce the number of black students attending the system's 108 majority-black schools, "you'd be doing some kind of hauling. Obviously, some could be made less black."

The increasing number of schools falling outside the court's 50 percent guidelines has been a matter of concern to the NAACP since 1975 when the number returned to the earlier 46. At that time the organization asked the school board to devise a new busing plan to bring all schools back under the 50 percent limit.

But so far, the civil rights organization has not sought to reopen the court case.