The nation's SAT math scores reached an all-time high, while verbal performance stalled and the results for Washington area school systems were decidedly mixed.

In results released yesterday, Virginia schools reported a 5-point increase in math, the largest gain by any state where a majority of students take the SAT. In Virginia, 73 percent of students took the test.

Maryland's scores were unchanged. Many school systems had nothing to report yesterday, owing to a delay in delivery of data from the test publisher, the College Board.

The 2005 SAT report marks the exit of the familiar two-part test, which yields a maximum score of 1600 points. Starting next year, SAT results for high school seniors will be reported on a third test, in writing, and another 800 points will be added to possible scores. The College Board provided a glimpse yesterday of preliminary average scores on the writing exam, which are slightly lower than verbal scores and considerably lower than math averages.

The two largest school systems in the Washington region, Montgomery and Fairfax counties, did not release SAT scores yesterday because a mailing glitch left them empty-handed. College Board spokeswoman Sandra Riley said the reports may have been delayed because they were sent from the Midwest, rather than New Jersey as in years past. She said the agency heard few reports of delayed test-score packages outside Washington.

In Prince George's County, where SAT data arrived on time, reading scores were flat and mathematics scores fell, to an average of 435 from 439.

"Without question, we have to focus on improvements that we need to make," said the interim schools chief, Howard A. Burnett.

Students in Howard County posted the highest scores the school system has seen. The composite score was 1113, a 16-point gain from last year. Superintendent Sydney L. Cousin attributed the gains to efforts to tailor instruction to students' diverse learning styles.

Loudoun County also posted its highest average SAT scores, with a combined score of 1073. It is the third consecutive year of increases for the county, which has been opening three to five schools a year for a decade to accommodate thousands of new students. Scores in the county rose at six of seven high schools and for every ethnic group. The combined score for Hispanic students jumped 69 points; the score for African American students was 21 points higher.

Among this year's college-bound high school seniors, the national average verbal score was 508, the same as last year. The average math score rose to 520 from 518. Math scores have risen steadily since the early 1990s, while verbal scores have stagnated since the middle of the last decade.

Only partial results were available from the District and the rest of the Washington region.

The College Board admonished educators nationwide to stress old-fashioned grammar and composition in the classroom, skills that they said had deteriorated in recent years.

The flat verbal score "reminds me that we have to keep an eye on the literary skills so important in college and later life," said Gaston Caperton, College Board president, in a news conference.

SAT scores offer a fairly good indicator of a high school's academic caliber in the Washington region, where participation in the exam tops 70 percent and continues to rise, officials say.

But many testing experts warn against using SAT scores alone as the measure of a school system, because such factors as household income and participation rates influence results.

Virginia's combined average score of 1030 exceeded Maryland's average, 1026, reversing their relative standing in 2004. In a decade, Virginia's math score has risen by 20 points and its verbal score by 12 points.

During a telephone news conference yesterday, Virginia Gov. Mark R. Warner (D) attributed the improvement, in part, to a rule in place since 2002 that requires students to take some advanced math classes to graduate with a standard diploma. Officials also cited increased training for math teachers and the state's recent addition of online Advanced Placement courses, which give students in rural areas access to a greater variety of advanced classes.

"I think it reflects the fact that in Virginia we have raised our standards, and the students in Virginia public schools have stepped up to meet those standards," Warner said. "This is great news for Virginia's students, but it's also great news for Virginia's economy because it says we're going to provide a well-trained work force."

Maryland also touted an increase in participation in AP courses. Overall, AP participation was up 11 percent, and participation among black students was up 12 percent.

The College Board's Caperton urged school systems to offer more challenging classes, such as calculus, to minority students, citing a persisting achievement gap on the SAT.

The gap between black and white students has widened nationwide in the past 10 years: Scores for blacks are rising, but scores for whites are rising faster. In math, the average score for black students has risen 9 points; the average score for whites has risen 15 points.

The gap persists partly because black students are still less likely than whites to take precalculus, calculus and physics, according to College Board data. Students who take those courses in high school tend to do better on the SAT.

The achievement gap between black and white students widened somewhat in Prince George's County this year. But more African American students were taking the test, "which is fantastic," Burnett said. Overall, the number of test-takers in the county rose to 4,517 from 4,203.

The achievement gap is narrowing in Calvert County. The average combined SAT score there was 1071 for whites and 894 for African Americans -- a difference of 177 points. The gap was 183 points last year.

"We have been engaged in schoolwide initiatives to support our African American students," said Cathy Page, coordinator of system performance.

In a Washington news conference yesterday, the College Board offered a glimpse of the new SAT writing test, first taken in March by mostly high-achieving high school juniors. Scores from the first three testing dates, held this year, averaged 516 on the 800-point scale, with 200 the lowest score and 500 the midpoint. Those 1.4 million students had average verbal scores of 519 and average math scores of 537.

College Board officials said the averages will decline between now and next August, because a broader range of students will have taken the test.

Staff writers Nick Anderson, Lori Aratani, Tara Bahrampour, Maria Glod, Rosalind S. Helderman, Ann E. Marimow, Ylan Q. Mui, Amit Paley, Josh Partlow and Ian Shapira contributed to this report.

Howard County Superintendent Sydney L. Cousin touted efforts to tailor instruction to diverse learning styles.