Despite a slight increase in Washington's white population, the number of white children attending the city's public schools has fallen sharply since 1977 after holding steady for the previous four years.

Last fall the white enrollment fell to 3,321, according to a new enrollment report -- 8 percent less than a year ago and 25 percent below the number enrolled in 1977.

Black enrollment in the D.C. school system also has declined steeply -- by 4.9 percent last year and 21.7 percent since 1977. The drop, to 89,160, is part of an uninterrupted slide that began in 1970 and is matched by a decrease in the city's black population.

Whites now make up just 3.5 percent of the city's public school students, compared to 3.7 percent in 1977.

There was a precipitous decline -- about 10 percent a year -- in the number of whites enrolled in D.C. public schools for two decades after desegregation in 1954.

For four years in the mid-1970s the decrease stopped as enrollment stabilized in mostly white neighborhood elementary schools west of Rock Creek Park.

Since then, though, the loss at many of these schools has been severe, while east of the park white enrollment has remained negligible even in neighborhoods such as Adams-Morgan, Dupont Circle, Mount Pleasant, and Shaw, which have undergone extensive renovation.

"What we seem to be attracting are single persons or those who are married without children," said Gan Ahuja, the D.C. government's chief demographer. "It's unfortunate, but it's a fact; D.C. is not attracting many whites with school-aged children, and many of those who do come have very small families. We're conjecturing here a bit, but many of the husbands and wives both work, and their incomes seem to be high enough so they can afford private schools."

D.C. school board member Wanda Washburn, who represents mostly-white Ward 3, said the drop in enrollment probably was caused by disruptions from budget cuts, complaints about the quality of teachers, and concern about discipline in junior and senior high school.

"My own daughter is just graduating from Wilson High," Washburn said, "and she's done well there, but many parents who have the options are not sitting still . . . I can tell you it's OK, but it's hard to convince others. They put their children in private schools . . . They're not willing to put their kids where they're mouths are."

From a low point in 1976 to the fall of 1980, the number of D.C. white children attending private schools rose by 1,994, or 29 percent, according to the most recent data available. Blacks in private schools increased by 7.6 percent over the the same period. In 1980, 71 percent of the 12,522 white D.C. children in kindergarten through 12th grade were attending private schools, compared to about 10 percent of blacks.

According to D.C. government estimates, the city's total white population rose by about 9,000 from 1975 to 1980 after falling by about 475,000 since World War II. The 1980 census counted 171,796 whites in the city, about 27 percent of the District of Columbia's population.

Since 1977 the drop in white enrollment has been substantial at most schools west of Rock Creek Park even though the neighborhoods remain overwhelmingly white. Just seven of these schools now have white majorities, compared to 11 four years ago. They are the only public schools with white majorities out of more than 170 in the city.

At Lafayette Elementary in Chevy Chase, for example, the number of whites dropped from 524 in 1977 to 305 last fall. At nearby Murch, the decline was from 383 to 285, while at Eaton School in Cleveland Park the white enrollment fell from 253 to 118.

Whites now make up 77 percent of the students at Lafayette and 73 percent at Murch, but at Eaton the proportion of whites has dipped to 48.6 percent, with black and Hispanic children from outside its regular attendance zone making up the difference.

Most Washington schools have neighborhood attendance boundaries, though children usually are allowed to switch out of zone if space is available where they want to attend.

At Wilson Senior High, located in a solidly white area near Tenley Circle, white students make up just 18 percent of this year's enrollment. The number of whites attending has dropped by almost 100 in the past four years.

Deal Junior High, near Wilson, is about one-third white, but all of the city's other junior and senior highs are virtually all-black except for the small School Without Walls, based near George Washington University, which has 137 whites among its 300 students.

Banneker Academic High School, which opened this fall near Howard University, has just two white students along with 294 blacks and one Asian, even though whites had been prominent among those pushing for a selective academic high school several years ago.

"That shows you all those fears that it would be taken over by the elite are groundless," said D.C. City Council member Betty Ann Kane, whose daughter is one of the two whites enrolled. "It's a good school, but there just aren't many whites there."