A new, optional seventh-period class for Arlington high school students is proving an unpopular elective.

The Arlington School Board, responding to arguments that students did not have enough room in their schedules for arts and humanities electives, voted 3 to 2 in February to offer the optional period at the county's three high schools in September. The classes would meet three times a week for 85 minutes after normal school hours.

At Wakefield High School, only biology -- one of 13 possible after-school electives -- has interested enough students to warrant offering the course, according to Assistant Principal David Jeffrey.

Seventy-eight students, including current eighth graders who will be at Wakefield next year, expressed interest in one of the after-school classes. But none of the other offerings -- in English, mathematics, chemistry, physics or history -- had an enrollment of 15, the minimum needed to form a class, Jeffrey said.

At Washington-Lee High School, none of the courses had 15 or more students sign up, said Principal William Sharbaugh.

Yorktown Principal Steve Kurcis declined to say how many students had chosen the optional seventh period, but a guidance counselor there said she believed there were enough students to offer a few of the classes.

Since the School Board's decision, students have argued in letters and at board meetings that the optional seventh period unfairly forces them to choose between another class and other after-school activities.

Students also complained that the classes, which would meet from 2:05 to 3:30 p.m., would make the academic day too long.

School Board member Dorothy H. Stambaugh, who supported the optional seventh period, noted that the board also voted to expand summer school and Saturday classes to allow more students to take electives.

The summer school catalogue for 1985 lists a range of academic classes, which meet five hours a day for 32 days and cost $180, for students who want to finish their requirements and leave room for electives during the school year.

Board member Simone J. Pace, who with Margaret A. Bocek voted against the optional period, said he was not surprised by the response.

"There's no way this is going to work," he said. "The majority of the board opted for half a solution, which is not a solution at all." Pace said he favored a mandatory seven-period day.