Arlington School Board members expressed reservations last night about the cost of sending Arlington students to a new science and technology school in Fairfax and questioned whether the new facility would have significant advantages over the curriculum already available in Arlington.

The magnet school, one of four in Virginia, will open in the fall of 1985 in Annandale. The Fairfax County School Board voted last month to open the school, to be called the Thomas Jefferson High School for Science and Technology, to students from Arlington, Loudoun and Prince William counties and the cities of Alexandria, Falls Church, Manassas and Manassas Park.

The total number of students accepted from a school district could not exceed the percentage that the district's school population represents in Northern Virginia.

By current enrollment figures that means Arlington students could contribute 7 percent of the magnet school's enrollment. Each district that agrees to participate will reimburse Fairfax schools at an estimated $4,500 a student a year.

Arlington School Board member Simone J. Pace questioned whether the advantages of Jefferson's science and mathematics curriculum would be worth a half-million dollars -- the eventual cost of sending 28 students from each grade level to the school and providing a bus and drivers to take them.

Helen Rebull, chairman of the Arlington schools' science advisory committee, also encouraged the board to get involved in the new regional facility.

"No door should be closed on the willing, interested and able student," she said.

Board Chairman Gail H. Nuckols questioned whether the advanced courses at the magnet school would differ significantly from those offered in Arlington.

She also expressed concern about the effect on advanced science and math courses if some of the brightest students were to leave.

The board voted unanimously to table a decision on participating in the magnet school until its Nov. 15 meeting.