The proportion of school-age children in Alexandria who attend private schools has dropped by 8 1/2 percentage points in the past decade -- a sign, said local educators, that the issue of "white flight" has given way to educational considerations.

James Akin, director of research, evaluation and planning for the Alexandria schools, said the change may show that race is not a major factor in school selection. "We would hope it would just lay this issue to rest," he said.

According to a study by Akin's office, the proportion of school-age Alexandria children attending private schools fell from 19.5 percent in 1977 to 11 percent in 1986.

The study notes that the decrease comes at the same time as a decrease in the availability of low-cost housing, eliminating the possibility that the change in enrollment patterns is attributable simply to a decrease in the number of students who can afford to attend private schools.

Public school officials attributed the wide range of special programs available in the schools to their ability to attract students. "We don't sense any longer that it's white flight," said board member Sandra K. Lindsay. "We're competing more on the academic development lines than anything else."

The statistics mirror patterns in the District and Prince George's County, where the public schools are winning back students who once attended private institutions.

In the past three years, 5,400 Prince George's students left private schools for public schools there. District school officials have noted a similar trend, although statistics are not available.

About 12 percent of school-age children in the country attend private schools, including religious institutions, school officials said.

Competition between private and public schools in Alexandria has been a focus of debate among board members and community activists for many years, particularly since the racial mix of the schools has broadened.

Three years ago, the board adopted minority achievement as its top priority, in part, board members have said, because it saw improved academic standards as one way to assure parents that the quality of schools would not suffer from the pressures of a growing number of disadvantaged children, many of whom are black.

Alexandria has one of the most economically and racially diverse systems in the area. As of June 1987, 45.8 percent of the students were black, 36.7 percent were white, 9.9 percent were Hispanic and 7.5 percent were Asian.

The new statistics, said board member Gene C. Lange, may indicate that the primary reason parents take their children out of Alexandria's public schools is not based on racial considerations but on the religious and selective social milieu offered by the private schools.

"The social and religious part of it can never be overcome," said Lange, who has kept track of the public-private school scoreboard. "These numbers here are pretty good actually. They certainly show that we're holding our own and that we're bringing people in."

Despite the overall decline in private school enrollment, a few public schools lost a significant number of students, a fact that school officials said was disturbing and puzzling. Francis C. Hammond Junior High, which is embroiled in administrative problems, lost 33 students. John Adams Elementary School lost 14 students to private schools.

Lyles-Crouch Elementary School in the southeast Old Town-Rosemont section of the city had the highest private school attendance. There, 23.5 percent of the students within the schools' boundaries went to private schools in 1986. Cora Kelly, in the northeast part of the city, showed the lowest private school attendance, at 3 percent of all school-age children.