An article in yesterday's Metro section incorrectly reported that the Manassas and Alexandria school systems have decided not to participate in Fairfax County's regional "magnet" school for science and technology next fall. Manassas will participate; Alexandria will decide Dec. 12.

The Arlington School Board voted last night not to participate next year in Fairfax County's regional high school for science and technology, deciding instead to concentrate on improving Arlington's own science curriculum.

With the unanimous vote, Arlington became the third jurisdiction to adopt a "wait and see" policy for the magnet school's first year. Alexandria and Manassas also will observe the school for the 1985-86 school year, but not send students there.

During an intense, hour-long debate, several board members indicated they were torn between the advantages for students who might attend the new school and the effect their absence would have on existing science courses.

The "magnet" school, one of four in Virginia, will open in the fall of 1985 at the existing Jefferson High School 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. School officials in Loudoun, Prince William and Falls Church already have decided to participate.

Under a one-year agreement between Fairfax and each jurisdiction that participates in the school, the total number of students accepted from a district could not exceed the percentage that district's school population represents in Northern Virginia.

By current enrollment figures, that means Arlington students could make up 7 percent of the magnet school's enrollment (42 students the first year and 112 eventually.)

Board members questioned last night whether a school that served such a small percentage of Arlington students would be worth half a million dollars -- the eventual cost of sending 28 students from each grade level to the school and providing transportation for them.

Several parents expressed concern about the effect on Arlington's science curriculum if many of the brightest students were to leave.

Marjorie Mayer, parent of two Washington-Lee High School students, argued that "short ration would occur if the 100 best science students were sent to the magnet school and the rest were left here with antiquated labs and equipment."

Board member Dorothy H. Stambaugh cautioned that sending students to Thomas Jefferson might not only drain money from Arlington's own curriculum but blunt the county's incentive to compete with model science programs.

"If we are taking a certain number of our most capable students and sending them elsewhere, we can become complacent about being on the cutting edge of providing the best science and math courses," she said.

Superintendent Charles E. Nunley, who recommended sending students to the magnet school, argued that a decision not to participate would deprive some of Arlington's most promising students of the chance to take advanced science electives and use state-of-the-art laboratory equipment. "I would hate to see Arlington students miss this opportunity," he said.

Don F. Brandewie, Arlington curriculum supervisor for science, said the county could not afford to match the financial support from businesses that has been pledged to Thomas Jefferson.

"We can not compete with all of those electives," Brandewie said. But he said Arlington could reshape some science courses to make them comparable with the magnet school's core courses of molecular biology and geoscience.