Prince George's County, under a court order to desegregate the area's second largest school system, apparently has met the initial court-ordered goals of having 80 percent of all students in "desegregated" schools this fall.

According to school-by-school enrollment figures released by the school system last week, 81 percent of the county's 103,000 students attend schools whose enrollments fall within numerical guidelines set out in a court agreement between the Board of Education and the NAACP. Specifically, those guidelines state that 80 percent of all students should be in schools in which black children account for no less than 10 percent nor more than 80 percent of the enrollment.

The enrollment figures are based on a Sept. 30 head count showing that 62 percent of the students in county schools are black, inching up from 61 percent a year ago.

Prince George's has seen a steady change in its student population in the past two decades. As the county's overall school population has continued to decline, peaking at 160,500 in 1970, the number of black children has increased. In 1979, black children accounted for 19 percent of the students in the county.

The school system faced drawing up a mandatory busing plan for the next school year if it had not reached this fall's goals. But school officials have long projected that they would meet the goals. Racial balance in schools has generally fallen within that range during the past few years.

The NAACP first filed a legal challenge to school enrollment patterns more than 15 years ago. Since reaching an agreement in 1985, the county has been under a federal mandate to desegregate its schools. A desegregation plan introduced that fall has centered on establishing magnet programs in special arts, science, mathematics, languages or the classics to lure students to schools outside of their communities.

While the majority of the 41 magnet schools are designed to attract white students to predominantly black schools, "reverse magnets" have been opened to improve racial balance at some predominantly white schools.

Most of those programs seem to be making an initial impact on racial balance, according to the county's data.

Twenty-four of the magnet schools met the court's goals and improved racial balance by enrolling more white children. Five schools improved their black enrollment.

Andrew Jackson Middle School, for example, opened with a classical studies program this fall. It attracted 30 students from other communities, enough to change the racial balance of the school from 88 percent black last year to 77 percent this fall.

Rogers Heights Elementary School in Bladensburg, which has a French language immersion program initially aimed at kindergartners, has seen an increase in nonblack students in its upper grades.

"Its attractiveness as a magnet school has helped enroll a larger percentage of nonblack students," school system spokesman Brian J. Porter said.

Twenty-eight of the county's 171 schools fell outside the court guidelines. Half of those were the compensatory or Milliken schools that are expected to remain as much as 97 percent black because of their distance from racially mixed communities.

Largo and Fairmont Heights High schools unexpectedly exceeded guidelines, officials said.

For the first time in recent years, they attracted student bodies that were just above 80 percent black. Officials said they had no immediate explanation, although housing development has been rapid in the Largo area.

Extended-day or work-place magnet programs at such schools as Apple Grove and Kettering Elementary, among the first magnet programs, have not proved to have a significant impact on racial balance. Enrollment at both continues to hover outside the court's initial guidelines at about 85 percent black enrollment, although magnet programs were opened there two years ago.

This is not to say the extended-day programs have not been popular. They are filled with pupils who need the before- and after-school care.

However, parents from other communities have not sought out the programs, school officials said.

They will be among the schools that educators will study this year as they undertake the first major review of the magnet programs.

School officials may adopt changes to magnet programs that have not been successful, officials said.

The court agreement sets as next year's goal having 85 percent of all students in schools where black enrollment falls within the 10 to 80 percent range.