Montgomery County students posted lower results this year than in 2004 on statewide high school exams in algebra, biology and government, according to scores released this week.

The High School Assessment exams (HSAs) are supposed to measure how well students have mastered key academic subjects. Scores from a fourth exam -- in English -- will be released in the late fall.

Beginning this fall, high school freshmen in Maryland will be required to pass the tests to earn their diploma.

This year the percentage of students in Montgomery County who posted passing scores in algebra, government and biology declined slightly from last year. In biology, 70.1 percent passed in 2005, compared with 73.8 last year. In algebra, 67.7 percent of students passed, compared with 72.4 in 2004. In government, the best subject for Montgomery County pupils, 77.3 percent of students passed, down from 79.1 percent passing in 2004.

Other area school systems, including Howard, Prince George's and Anne Arundel, posted mixed results. In Howard County, the percentage of students passing government and biology declined slightly, while the number passing algebra increased by a small percentage.

Drawing conclusions from the overall numbers in Montgomery County is difficult because there has been no consistent pattern of gains or declines since students began taking the exams in 2002. School officials also say that they can't be certain that students are doing their best on the exams, because the scores will count toward graduation beginning only with this year's freshmen.

Still, even if students are not taking the exams seriously, an analysis of scores by race and by category of students (special education, limited English proficiency, free and reduced-price meals) reveals the same achievement gaps found in other measures of performance.

The passing rate among black, Hispanic and special-education students was significantly behind those of their white and Asian counterparts. American Indian/Alaskan Native students post scores that are higher than blacks and Hispanics but below those of whites and Asians.

In special education, fewer than half the students had passing scores. Only 28.7 percent of the special-education students passed the algebra exam. In biology, 32.5 percent of students passed, and in government, 40.9 percent of the students passed.

If the patterns persist, officials in the state's largest school district could find themselves scrambling to create programs to help students pass. Brian Edwards, a Montgomery County schools spokesman, said that it is too early to be considering interventions and that officials need a better understanding of how students are faring.

Overall, Montgomery County students with limited English proficiency were the only group to show gains for four consecutive years on the government test. In 2002, 26.4 percent passed the government test; in 2005 that number increased to 45.6 percent.

Students across Maryland began taking the exams in 2002. Although the tests are called high school assessments, students may take the exams in middle school when they complete algebra.