A majority of the D.C. public elementary and junior high schools improved their performance on standardized reading and mathematics tests this year, and the city's third graders met national norms for the first time since the testing program began five years ago.

The city's high school students did not perform as well. Their scores stayed the same or dropped somewhat in most cases, prompting Schools Superintendent Floretta D. McKenzie to call for more reading and math courses in high schools.

Test results for grades three, six, nine and 11--key levels in a student's education--were released last week. The lowest scores were at grades nine and 11, where students lagged from one to nearly three years behind the national norms.

The tests, known as the Comprehensive Tests of Basic Skills, measure the reading and math skills students have mastered in a given school year. The scores provide "the truest, most open way to demonstrate how good" a school system is, Associate Superintendent James T. Guines said.

Third graders as a group scored 3.9 in math, or one month above the national norm of 3.8. They were even with the norm in reading.

That score refers to third grade, eighth month. Because the tests are given in May, the ninth month of the school year, students who are working at grade level are expected to receive a score of 3.8 or better. The norms for the other grades are 6.8, 9.8 and 11.8. These norms represent the average or typical performance of students in the country as a whole in those grades.

The District's sixth graders fell somewhat short of the norm, scoring 6.6 in math and 6.2 in reading. Ninth graders hit 8.7 in math and 7.9 in reading. Eleventh graders scored 9.2 in reading and 9.0 in math.

School officials credit a "back-to-basics" program of instruction called the competency-based curriculum (CBC) and the school system's new, stiffer promotion standards with reversing the longstanding trend of low achievement in District schools. Test scores have been rising for the past five years since the CBC was initiated.

McKenzie also attributed improved junior high scores to a recently instituted "intensive junior high program" that requires students to take more reading and math courses.

Sixty-three of the city's 127 elementary schools matched the national norm for reading, and 88 reached it in math. On the sixth grade level, 31 schools were at or above the norm in reading, and 47 achieved or surpassed it in math.

Of the 39 schools where ninth graders were tested, only seven achieved the norm in reading and six reached the norms in math.

Only two high schools--Eastern, at East Capitol and 17th streets SE, and School Without Walls, an alternative program for outstanding students--reached national norms in reading. Only School Without Walls and Wilson, at Nebraska Avenue and Chesapeake Street NW, achieved the norm in math.

The top scoring high schools were School Without Walls--students of which take classes at local museums and institutes--and the Banneker Academic High School, at Georgia Avenue and Euclid Street NW, where ninth graders scored at college level in math.

Eastern was among the high schools that showed the greatest improvement from last year. Its 11th grade reading scores were up from 8.5 last year to 11.8 this year, while its math scores rose from 8.7 to 9.9.

This year, scores for science and social studies tests also were released. Students generally did more poorly in those areas than in reading and math, which are the primary focuses of the competency-based curriculum.

As a result, McKenzie vowed to strengthen the instructional program in both those areas, especially at the junior and senior high levels.