At least half the students at 13 D.C. elementary schools scored at or well above grade level on math and reading tests last spring. But most youngsters at the roughly 130 other schools continued to lag behind where they should be.

The school-by-school Stanford 9 achievement test results released yesterday highlight a continued, jarring divide in the school system of the nation's capital.

Most of the more successful schools are in affluent, majority-white areas west of Rock Creek Park where students have traditionally done well. But they also include Burrville Elementary in far Northeast, where test scores have improved dramatically in the past two years, as well as historically strong Shepherd Elementary on upper 14th Street NW and Thomson Elementary downtown.

At the top-scoring school, Horace Mann Elementary in Ward 3, more than half the students scored at the "advanced" level.

But most elementary schools--and almost all secondary schools--posted few or no advanced scores. Large numbers remained mired in "below basic," the lowest level, although most schools are slowly moving youngsters into "basic," or low-grade level.

"If we look at achievement overall in urban systems, it's in crisis, and that's what reform is all about," said Searetha Smith, associate superintendent. "I see steady progress. The data is indicating that we're on the right track."

Even at some low-scoring schools, there are successes. Randle Highlands Elementary in Southeast boosted its rate of students at the proficient level from 22 percent to 38 percent in the past two years, and cut those scoring below basic from 23 percent to 9 percent. There, as at most schools, scores jumped sharply from 1997 to 1998, but held steady or changed only slightly last school year.

Officials for the first time released test results broken down by ethnic group, which showed the system's few white students scoring overwhelmingly in the top two categories. Asian and Hispanic students scored mostly at grade level early on, but their scores declined in high school. Black students scored primarily basic and below basic in most grades.

The test results are used to evaluate principals and reward schools that improve with bonus money. They are also a factor in deciding which elementary students are promoted.

But they will have grave consequences for students entering senior year in September 2001. To receive a diploma, students will have to score at least at the basic level on the 11th-grade exam--or pass a separate proficiency test that has not been unveiled.

Nearly half this year's 12th-graders scored below basic on the 11th-grade reading test last spring. Three of four scored below basic on the math exam.

Smith said officials will begin educating the public "within the next few weeks" about the new requirements. Virginia and Maryland also plan to link graduation to standardized test scores, though not as soon as the District.

About 22,000 of the system's 72,000 students did not take the Stanford 9 tests last spring. More than 17,500 were exempt because they were preschool, kindergarten, 12th-grade or nongraded students. Some of the rest had language or learning difficulties that precluded them from being tested. Smith said she would check to see if others should have been tested.

Complete results will be posted this week on www.washingtonpost.com and included in the Oct. 21 District Weekly.