The Montgomery County school board last week imposed a tough new requirement that would place students who are ready to enter junior or senior high school but are behind in their work in special remedial classes. They would remain in the classes until their performance is up to grade level.

The rule is aimed at students who already have repeated the sixth or eighth grade and still are working below their level in reading or math.

The program was proposed by board member Marian Greenblatt, who charged that "substantial numbers" of students who could not read or compute were graduating. "We have a problem and we have to deal with it," she said. "It's not fair to the students, to their parents or to society."

Board members Joseph Barse, Suzanne Peyser and Eleanor Zappone agreed with Greenblatt and voted, after a lengthy debate, to approve the proposal.

The board's decision on remedial classes is part of a broad new policy for grades kindergarten through eight. It is designed to make the school system's academic program much tougher.

Last month the board also tentatively approved a crackdown on social promotions. Under that provision, also proposed by Greenblatt, principals would have to justify in writing the promotion of any student who was below grade level.

Greenblatt said she proposed the remedial program, which would be held in every junior and senior high school, to strengthen the entire academic program. When students lag behind, she said, the regular curriculum gets "watered down" to accommodate them.

In addition, she said, "these students usually have discipline problems because they can't cope with the material."

As an indication of how widespread the problem is, she cited figures from Blair High School in Silver Spring in which 300 of the school's more than 700 students are two years or more below grade level in basic skills. Under next year's budget, Blair will receive more than $300,000 to upgrade its academic program with particular emphasis on programs for students who are deficient.

Under the new policy, students will be required to enter remedial classes if they have failed a year and teachers and principals determine they are still at least a year below grade level in reading or math. Their test scores also will be part of the evaluation.

The students may not be removed from the special classes until they are judged capable of doing grade-level work along with their classmates. Although the subjective judgments of teachers and principals will be taken into account, the majority of board members insisted that objective standards such as test scores also be used in reevaluation.

Some critics of the proposal had argued that Greenblatt's original language for both the social promotions policy and the remedial program had relied too heavily on students' performance on test scores.

They charged that ignoring staff recommendations for children would have made the policy too rigid.