Evelyn Reid Syphax, the new chairman of the Arlington School Board, said yesterday that the county's 11-year-old voluntary school busing plan has become "outmoded and inappropriate" and should be changed.

Syphax, who is black, said the court-approved plan "was drawn up in and for the Arlington of an earlier day and cannot be defended on any ground having to do with instruction or curriculum. All schools today are supposed to be good."

If her suggestion is approved, it would mark one of the first major modifications of the 1971 plan that called for busing to desegregate what were two largely black elementary schools. That plan provoked much controversy in the county, which in 1959 had become one of the first localities in Virginia to integrate its schools.

The new school board chairman said in an interview yesterday that while she had no specific proposal in mind, her suggestions likely would transfer more black students to neighborhood schools. Under the current busing plan several hundred students from a predominantly black neighborhood in South Arlington are bused to schools in the more affluent northern and central parts of the county.

Syphax said yesterday that Arlington has changed considerably since 1971 when it sought and won federal court approval for that plan. "The plan was drawn up in the days when we wanted to achieve integration, but the demographics in Arlington have changed so much since then," she said. "We have other minorities to consider, but we're not busing other minorities. We need to take a look at the situation."

During the past decade, overall enrollment in the county schools has plummeted from 23,512 to nearly 14,500 students. At the same time the numbers of Asians and Hispanics, who in 1971 were only 2 percent of the enrollment, have grown rapidly. Today Asians represent more than 14 percent of Arlington's students and Hispanics, 8. Blacks, who then were 11 percent of the students, now account for almost 16 percent and white students, who were 84 percent, now are 62 percent.

Syphax said she wants the board to consider the busing issue as it deliberates school closings and revisions to school attendance zones scheduled to be implemented in September 1984.

"If we change the system, there are probably some children who would return to neighborhood schools, and I hope this would happen because we have little ones being transported all across Arlington and it's just too much for little ones," said Syphax, a former public school teacher who operates her own preschool education center.

Syphax, who this week took charge of a five-member school board composed of Republican appointees, is not the first to suggest a review of Arlington's busing plan. A commission that has been studying secondary school consolidations raised the issue in an interim report last February. "Does the busing now imposed on certain black students make sense for the future in light of the declining numbers of blacks and the growth of the other minorities?" the report asked.

Most county officials could not be reached yesterday for comment on Syphax's proposal. County board member Ellen M. Bozman, a Democrat-backed independent, said that Syphax "has a deep, abiding concern and knowledge that none of the rest of us have about how it busing affects black children. If she feels it is a question that should be looked into, then she is very likely right."

In the past some Arlington school officials have questioned whether the board can adopt changes to the busing plan without court approval. Syphax said she would not object to taking the issue back to court. "It's one approach and it's probably the best," she said.

School Board Vice Chairman Simone J. (Sim) Pace said he sympathizes with Syphax. "I think the parents are more concerned about the quality of the schools than racial balance," he said. "I see us going into this process with our eyes wide open and with racial balance one of several elements we have to consider."

In 1971 the board was under strong pressure from the black community to desegregate Drew and Hoffman-Boston elementary schools, the last two overwhelmingly black schools in Arlington. The school board then agreed to close the two schools as conventional neighborhood schools and began busing the students elsewhere.

When the desegregation plan was unveiled, the black community and segements of the white community fought it in federal court because only black students were to be bused. District Judge Oren R. Lewis rejected their complaints and approved the plan.