Reading and mathematics test scores in Washington's public schools rose significantly last spring for the first time in a decade, Superintendent Vincent Reed announced yesterday.

The increase in score averages, which came in a school year disrupted by a 23-day teachers' strike, occurred in all three grades tested. The scores for two of the grades - third and sixth - are higher than they have been at any time since 1971.

However, most of the scores were still well below national norms.

Ninth graders lagged almost three years below the norms in both reading and mathematics.

Sixth graders, who made the sharpest improvement, averaged five months below the norm in mathematics and 1.2 years below in reading.

Third graders were just two months below the norm in mathematics and six months below in reading.

School administrators said yesterday they did not yet have the detailed information needed to explain the new test results.

"We don't have a complete report yet," said J. Weldon Greene, director of program development who supervises testing. "And that makes it kind of difficult to analyze the reasons why this (improvement) happened."

But Greene noted that school officials were "very happy about it, and we thought the (school) board and the public should know."

The results released yesterday are from tests given in early May to all third, sixth, and ninth graders throughout the city. The multiple-choice exams, called the Compenhensive Test of Basic Skills, were prepared by the California Testing Bureau, a division of McGraw Hill Publishers. Testing time for the reading and mathematics tests combined was about three hours.

The sixth grade made the sharpest improvement in scores, averaging five months higher in both reading and mathematics than it had a year earlier. Third graders averaged two months closer to the national norms than they had been in 1978. Ninth grade averages improved two months in reading and three months in mathematics compared to a year earlier.

Reed announced the results in a brief press release but could not be reached for comment.

However, Greene said the improvement may be the result of the school system's competency-based curriculum, which stresses step-by-step instruction in specific skills. The curriculum was used in about a third of the city's 180 schools last year.

He said it may also be a response to the emphasis Reed has put on improving test results and the test score targets that the superintendent set last fall.

Greene said a full report, showing school-by-school results, the number of children tested, and detailed comparisons between Washington pupils and those across the country, will be issued in about a month enabling school officials to draw better conclusions.

During the last few years, D.C. test scores generally drifted lower or stuck at low levels. In 1975 and 1976, when the tests were given to a 10 percent sample of pupils in grades 1 to 9, there were gains reported in mathematics or reading in some grades but in other grades the scores went down.

This spring the test scores were up in both reading and mathematics in all three grades tested.

The grade-level norms on the standardized tests are based on the scores of a representative national sample of about 130,000 students who took the exams in 1972 and 1973.

Since then scores throughout the country have improved slightly up to third grade but have declined among older pupils.

Yesterday Greene said he was particularly happy with the results for Washington's sixth graders because the tests at that level require pupils to demonstrate analytical and comprehension skills, and apply basic material they were supposed to master in lower grades.

The junior high tests require even more analytical skills, and Greene said the relatively low scores for ninth graders were a cause for "serious concern."

"We're very pleaded to see (the scores) increasing, instead of going down. But we still have a long way to go," he said.

Under pressure from the school board for improved academic performance, Reed announced last November that he was setting specific test score targets for the May standardized exams.

Although his "ultimate goal" was for city students to reach national norms, Reed said he felt interim targets would help the school system get there.

"That was very important," Associate Superintendent James T. Guines said yesterday, Reed, he said "was telling people: 'Do what I really want, a very simple thing: Improve the test scores in reading and mathematics.' And boom - that's what happened."

The average reached the target for third-grade math and were close in third-grade reaching and in both subjects in sixth grade. But the scores for ninth graders were one year below the goals Reed set.

"If we didn't have the strike, who knows how well we could have done," Guines said. "Obviously the strike hurt us, but I think we recovered."

After the teachers' walkout had disrupted schools for most of March, the school system revamped its elementary and junior high classes to give more time to reading and mathematics. There also were voluntary make-up classes an hour before and after regular sessions.

Guines said the competency-based curriculum, which is spelled out in a massive set of detailed curriculum guides, will be used in every D.C. school this fall. The program also involves setting strict standards, based on test scores, for promotions from grade to grade, but Guines said these have not yet been established.

The school system began developing the new curriculum in the spring of 1976, about six months after Reed became superintendent.