Montgomery County students will have to take an intelligence or "ability" test as usual in April, the county Board of Education decided this week.

Concluding that an imperfect test is better than none, the school board voted 5-1 in favor of using the controversial Cognitive Abilities Test at least once more.

Edward Andrews, interim superintendent, had proposed that the test be dropped because, he said, the scores are unreliable and test results are misused.

The test, given to students in grades three, five, seven, nine and 11, is intended to measure a youngster's academic potential.

The scores are used for placement of students in classes geared to their individual learning abilities. Taken together, the scores also are considered a method of measuring a school system's success.

Yet, Andrews said, schools are not sure what the test measures.

"I do think it is misused," Andrews said at last week's board meeting. "Any use is dangerous -- some youngsters are injured by its use."

Teachers tend to expect too little of pupils who score poorly on the test, Dr. Joy Frechtling, director of the division of program monitoring, said after the meeting.

"I'm concerned with kids on the lower level," Frechtling said. "A teacher can look at a test and say, 'That score is (low); we're doing as well as we can.' The goal should be to raise a child's scores."

Board member Joseph R. Barse said he believed, "It would be a mistake to do away with what we have (the test) without seeing the package that will replace it."

No replacement test was proposed. Steven Frankel, director of education accountability, said scores on achievement tests, records, classroom work and teacher recommendations could take the place of the Cognitive Abilities Test scores in placing students in special programs.

The board's vote to use the test one more time was a preliminary one, but it appears unlikely to be reversed when the issue comes up for final action Feb. 12.

A county committee of educators recommended last fall that the test be dropped in 1981 and, Frechtling said, "We thought, if there are doubts about it for next year, why give it this year?"

Dropping the test would have saved the students the two hours they must spend taking it, and would have saved the county school system $80,000, Frechtling said.

In other actions, the school board unanimously adopted a policy for teaching foreign students.

The new rules, intended to ensure equal education opportunity regardless of language background, require that a student be instructed in his native language and also attend English classes. A student would be transferred to classes taught in English once he knew the language well enough to succeed.

Montgomery County has an estimated 2,200 foreign-born students who speak a total of 40 languages. In each of 144 county schools, at least one student does not speak English well enough to learn without special help.

The school board also voted its opposition to a proposal in the Maryland General Assembly that would tie state payment of a portion of county teachers' Social Security taxes to an equalization formula. Under the plan, more money would go to poorer counties, while affluent Montgomery would lose.