In a major shift from the pattern of many decades, more black students are attending public schools this fall in the Washington suburbs than in the city.

The new enrollment fugures -- 98,462 black students in the Washington suburbs compared to 93,756 in the D.C. public schools -- are sharply different from those of 10 years ago, when blacks in city schools outnumbered blacks in the suburban schools by almost 2 1/2 to 1. This is the first year that blacks in suburban schools exceed those in the city.

Overall, the number of blacks decreased 32 percent in city schools during the decade, while the number attending schools in the suburbs rose 68 percent.

The figures are a sign of one of the major trends of the 1970s -- the massive movement of blacks from city to suburbs, particularly of middle-income families with children. The Washington area is one of the main centers of this movement, but demographers say similar moves have occurred around New York, Cleveland, Atlanta and other large cities, although the extent of the change will not be known until the 1980 census is reported.

"It's really quite remarkable," said George W. Grier, a demographer who has studied population trends in the Washington area for the Greater Washington Research Center. "Blacks used to be overwhelmingly concentrated in the District of Columbia. But that's not true any more."

The main factors in the move of blacks to the suburbs, Grier said, were the local and federal open housing laws passed in the late 1960s, which banned discrimination in the sale or rental of housing, and the rise in black incomes, particularly of families.

"The kind of housing that's offered by the suburbs is primarily family housing," Grier said. "And the blacks who are moving seem to be doing it for the same reasons as the whites who moved before them. They want play space for their children and schools that are regarded -- correctly or incorrectly -- as good."

"They came because of the search for the dream," said Bonnie Johns, a black member of the Prince George's County school board, "for better schools -- they think, for better communities, for the opportunity to participate in the community process. Once they're here, the dream is not as real. But overall, I think it's for the better. You don't have people cloistered in little separate groups as much as you did, and I think that's good."

Although almost 65 percent of the black students in the suburbs are in Prince George's County, the percentage increase over the decade was greatest in Fairfax County schools, where black enrollment grew by 102 percent, from 4,214 in 1970 to 8,530 this fall.

Even so, Fairfax still have the smallest proportion of blacks, 6.7 percent, of any major jurisdiction in the area. But that proportion is up from 3.2 percent in 1970.

Overall, the number of blacks attending schools throughout the area fell by 2 percent from 1970 to 1980, as births and migration from elsewhere in the country declined.

But the number of white school children in the area dropped by much more -- a 29.5 percent decrease over the decade. The decline was caused partly by a major decrease in births, Grier suggested, and by the movement of many white familes with children to counties on the fringes of the official metropolitan area, such as Howard County in Maryland and Stafford County in Virginia.

Despite reports of an increase in the white population of the District, the number of white children in D.C. public schools has continued to decline, indeed at a slightly faster rate than the loss of blacks. Although the white enrollment appeared to stabilize at about 4,400 from 1975 to 1977, it has fallen by several hundred each year since then, including a drop of 343 this year -- down to just 3,611 or 3.6 percent of the D.C. public school students. In 1970 the D.C. public schools had 6,496 white students or 4.5 percent of enrollment.

However, the numbers involved in the decline in blacks were much greater as black enrollment in the city schools dropped by 43,746 over the decade, including a loss of 5,854 this fall.

The data on fall 1980 enrollments comes from official reports of the different school system. The 1970 figures were compiled by the federal Office of Civil Rights, now part of the U.S. Department of Education.

Reports for indivdual schools show a continued spread of blacks into mostly black areas, particularly in Prince George's County. At the same time, smaller though substantial numbers of blacks are moving into areas, particularly in Montgomery and Fairfax, where hardly any blacks lived a decade ago.

Overall, the number of blacks in the Montgomery school system rose by 85 percent over the decade to 11,912 this fall. As a proportion of total enrollment blacks increased from 5.1 percent of Montgomery's students in 1970 to 12.1 percent in 1980.

In Prince George's County, the number of blacks went up by 90 percent since 1970 to 60,793 this fall. Over the same period, blacks increased from 19.9 percent to 49.9 percent of all Prince George's students.

During the last four years, though, the increase in black enrollment in Prince George's schools has slowed considerably -- from 3,692 in 1976 to 592 this fall. But the increases in most other -- less heavily black suburbs -- have steadily continued.

The loss in white school children over the decade varied considerably in different suburbs. The sharpest declines occurred in Alexandria and Prince George's -- 64 and 56 percent, respectively. Both of them had massive busing plans for desegregation. However, Arlington -- with neighborhood schools and black enrollment that fell by 11 percent over the decade -- lost 53 percent of its white students from 1970 to 1980. The white decline in Montgomery was 33 percent; in Fairfax County just 14 percent.

Grier said all the close-in counties lost white students partly because of the transformation of what had been family neighborhoods into areas dominated by singles and childless couples, whose numbers surged during the decade.

The only parts of the metropolitan area with a substantial increase in white students were the counties farthest from the center -- Charles, Loudoun and Prince William. However, even in them white enrollment has fallen a little over the last three years.

In Charles and Loudoun the number of black students dropped slightly over the decade, apparently reflecting the continued migration of rural blacks to the cities.

Throughout the area the number of Asian and Hispanic students rose substantially, though they still make up only 5.5 percent of total enrollment compared to 35 percent for blacks and 59 percent for whites. The increase in Asians, many of them Vietnamese and Korean, was much greater than the rise in Hispanics. Asians now outnumber Hispanics by 19,627 to 11,115. The largest increase in Asian students occurred in northern Virginia -- in Arlington up to the mid-1970s and more recently in Fairfax County, which has become far more polyglot than it was at the start of the decade.

No complete data is available on the racial composition of private schools in the area, though traditionally they have been heavily white. Total private school enrollment fell in the early 1970s, principally in Catholic schools, but it stabilized late in the decade.