The Arlington School Board, in response to vigorous lobbying by county teachers, last week unanimously adopted a plan for the next school year that would continue to give teachers weekly planning time by releasing students early.

The teachers, who had packed the board room at the Arlington Education Center, asked the board to continue the early-release program so that the extra time they spend at school could be used for planning. Elementary teachers currently release students early on Wednesday, at about 12:30 p.m., and use the rest of the day for planning classroom activities. The early release allows teachers a block of more than four hours for such chores.

Superintendent Larry Cuban recommended to the board in March that the planning time broken down into 25-minute segments throughout the week rather than the four-hour block on Wednesdays.

Teachers appearing before the board, however, said Cuban's recommendation, although it provided more planning time for teachers over the school year, did not meet their needs and adked the school board to seek a variance from a 1977 state law, which mandates instructional time.

Under the 1977 law, students are requirred to spend 27 1/2 hours with the teacher during the week with a minimum of four hours a day spent in school. Arlington's teachers spend the requirred total time with students each week, although they do not meet the minimum of four hours on Wednesdays. The school system had received a variance from the state for the early-release program for this year.

After offering a motion that the board accept an early-release calendar - which provides for students' early release on 24 days of the school year and 10 days for parent-teacher conferences - instead of the superintendent's recommendation, Board Member Mary Margaret Whipple said, "I'm convinced by the teachers . . . that the block of time is a more effective time."

Board Member Richard Barton favored Whipple's motion, but he cautioned teachers that the issue was being misinterpreted by many community residents and warned then that their help would be needed to explain the program to taxpayers.

"Somehow we have not got the message across that this is an educational tool," Barton said. "We're going to need your help to convince the community that you are not running away from the students."

The details of the schedule are expected to be worked out by the school administration and presented to the board at its next meeting. The schedule will, however, require state variances for the parent-teacher conference days.