Just as a new school year has begun, D.C. public school officials have released the school-by-school results on national achievement tests last year, scores that in most cases showed little if any improvement over the previous school year.

Scores for elementary school students slipped in most areas but, for the most part, remained above the national median. Junior high scores, long a focus of concern among city officials, posted modest gains and some declines. And most city high school scores either remained the same or improved slightly, but still averaged below the national median.

The yearly achievement tests are one of many quantifiers used to gauge student performance, but they are considered an indication of how classrooms are working and often used to judge the performance of a system's superintendent.

Year-by-year fluctuations are normal, said city officials, who registered disappointment when this year's citywide results were published earlier this summer.

In the 1988-89 school year, the scores jumped five to six percentage points over the previous year, a leap that was hailed as a sign of substantial academic progress in city schools. The most troubling movement in the 1989-90 results was the slight decline in scores in all subjects in elementary school. In previous years, those students have traditionally fared best on national tests.

Most high school scores continued to inch forward. Junior high scores remained largely the same.

In the early 1980s, test scores from city schools rose routinely until 1987, when the system switched to a new version of the Comprehensive Test of Basic Skills. The switch led to a sharp decline, which is common after a change. They remained unchanged the next year, then began to move up in all categories in 1988-89.