The Virginia Board of Education today unanimously adopted a major overhaul in the state's public school curriculum, mandating tougher standards for high school graduation, fewer electives and more required courses in mathematics, science and foreign languages.

The new plan, which will take effect in the fall of 1984, also creates a controversial "advanced studies" diploma for college-bound students that was pushed by Gov. Charles S. Robb but which many Northern Virginia officials have denounced as a return to academic elitism.

Board members today hailed the changes as putting Virginia "at the forefront" in a nationwide push for quality education. The changes, originally proposed earlier this year by state School Superintendent S. John Davis, include many of the recommendations that the National Commission on Excellence in Education mentioned in its recent report that condemned a "rising tide of mediocrity" in the public schools.

"We're one of the states in the country that is leading the way," said board member Margaret Marston of Arlington, who also served on the national commission.

Under the new plan, college-bound students starting the ninth grade will enter a rigorous program that will require three years of math, three years of science and three years of foreign languages. Currently, the state only requires one year of math, one year of science and no foreign language to receive a high school diploma. Elective courses would be dropped from seven, the current requirement, to four under the new advanced studies program.

Students who complete this program with an average grade of "B" or better, will receive a special gubernatorial seal of "special recognition" on their diplomas.

High school students who do not enter the advanced studies program should find their course load lighter, but tougher. Overall requirements for graduation will rise from 18 units of study to 20 units for students entering high school in the fall of 1984. Those students will also have to take at least two years of math, two of science and another year of either math or science.

The advance diploma, which will require 22 units, will be available for students graduating in the class of 1985.

The plan is likely to have a significant fiscal impact on many school systems throughout the state. The board has estimated that it will cost $11.6 million to implement the new standards, including $5.3 million to hire 217 more science teachers, $2.4 million to hire 99 more math teachers and $3.8 million for more laboratories and supplies.

There were indications today that the plan could cost much more than that and force some localities to raise taxes. Officials in Fairfax County, which has the largest school system in Virginia, said that while the state estimated the new standards will not add to their costs, they will actually have to spend as much as $2.5 million to hire additional teachers and construct 44 new science and math labs at $32,000 a piece.

Mary E. Collier, chairman of the Fairfax County School Board, said she was "terribly disappointed" by the state board's action and accused Robb of using Virginia's school children for "political" purposes. To fund changes required in the plan, "we'll have to go to our local taxpayers.

"We're glad to do it for our students. . . but not because somebody sitting in Richmond decides that's what is best for everybody in the county," said Collier.

At the heart of the county's objections are fundamental philosophical differences with state officials, particularly over the adoption of the "advanced studies," or college preparatory program. Robb and Davis, a former Fairfax County school superintendent, have promoted the idea as a means of instilling a sense of academic excellence that will prepare students for an emerging world of high technology and computers.

Opponents have charged this will stigmatize students who do not enter the program and receive a conventional diploma. By reducing elective courses, such as fine arts or music, critics say it will restrict the choices available to students and limit their exposure to the humanities.

Marston said the new graduation requirements will not be felt as "drastically" in Northern Virginia as elsewhere because many of the area's school systems, including Arlington and Alexandria, have already moved to increase graduation requirements. (Fairfax, which requires 18 units for graduation, is a noteable exception.)

Immediately after today's vote, Marston and Davis agreed to begin an investigation into elective courses offered by many schools with an eye toward reducing many that are "frills." Among those that are offered in some of Virginia schools are courses in "Sign Painting," "Barbecue Cooking" and "Knitting and Needlepoint."

"We have over 4,000 elective courses offered in Virginia and we don't even know what they all are," said Marston.

Today's vote by the state board was a crucial victory for Robb, who has made quality education a central theme of his administration and has lobbied the board to approve the proposals. Robb aide Timothy Sullivan said the governor has already begun discussions with Davis to design the new advanced study's seal as a "symbolic representation of the governor's office."

Asked about Collier's charge that Robb was using this for political purposes, Sullivan replied: "The governor's commitment to education is based on his belief in its absolute fundamental importance to the future of Virginia."