Public school officials and high school students in Southern Maryland had a glimpse last week at just how high the stakes could be in the state High School Assessment exams.

Ninth-graders starting high school this month will have to pass the tests in four subjects before they can receive diplomas in 2009. If that rule applied today, it is possible that a significant percentage of students would fail to meet the requirement.

Results for three of the four subjects covered by the exams -- biology, government and algebra -- were released Tuesday. Scores from the English exam will be available this fall.

After two consecutive years of improving scores, the percentage of Charles County high school students who passed the statewide tests declined this year in all three subjects.

In St. Mary's County, scores dropped slightly in biology and government and rose in algebra.

In Calvert County, officials' celebration of a 25-point jump in the percentage of students who passed the government exam was muted by the results in algebra and biology, in which scores fell after two years of improvement.

Charles County Superintendent James E. Richmond said last week, "I'm not happy, but I'm not shocked."

"We'll get there. We'll measure up," he said. "We've got great teachers and great students. We just have to get everyone on the same track."

There were two exceptions to the downward trend. At Lackey High School, 35 percent of students passed the algebra exam, compared with 28 percent last year. At McDonough High School, the percentage of students who passed the biology test increased slightly, from 65.7 percent to 65.9 percent.

Some of the deepest dips in Charles came in algebra, in which the passing rate dropped from 54 percent to 29 percent at Westlake High School, for instance.

John H. Cox, assistant superintendent for instruction, said algebra has been problematic in the past, especially the data analysis section, which asks students to solve equations for an unknown.

"That's a higher-level skill, so we have to see how that part of the test worked out," Cox said.

This summer, Charles teachers worked to develop programs meant to improve scores. Algebra, government and biology teachers were given new laptop computers and high-tech projectors programmed with sample tests and model lessons. More high school students will be enrolled in double periods of Algebra I.

Charles Board of Education Chairwoman Margaret Young said she was waiting for more information to determine whether the scores reflected a statistically significant drop.

"We can celebrate every time we get a little blip upward and we can chew our nails every time we get a little blip down, but the nature of testing is there will always be fluctuations up or down," she said. "You're not testing the same students every year."

Cox said he was somewhat heartened to see that statewide figures had followed a similar trend. The falling numbers, he said, could be attributed to inconsistency between test material from one year to the next or to the attitudes of students who knew last spring that the scores would not prevent them from graduating.

He said scores could get a boost from a change in student motivation when the results matter.

"Now it counts," Cox said, "so we think that's going to help improve the scores as well."

Students take the tests as they complete courses in each of the four subjects measured in the assessment program. Those who fail will have several chances to retake the exams. State officials said that by 2009, when passing will be mandatory for graduation, half the states will have implemented such exit exams.

Despite the drop-offs in St. Mary's County scores, school officials said they were encouraged that their high school students surpassed the state averages in all subjects.

And they said St. Mary's improved by 4.5 percentage points in algebra, even though the total passing rate in that subject -- 58.3 percent -- was well below those of the other subjects.

"We think we're on track. We have been working very hard to provide the teachers' curriculum maps and guides for their teaching," said Charles Ridgell, director of secondary instruction and school improvement. "The only thing I'm really concerned about is that students and parents realize . . . students do have to pass the High School Assessments in order to be able to graduate four years from now."

The lowest scores in St. Mary's were at Great Mills High School, where government was the only subject that more than half of the test-takers passed. In biology, 43.3 percent passed, down 13.1 percentage points from last year.

One of the priorities of the new superintendent, Michael J. Martirano, is to close the achievement gap between white and minority students, but on these tests, the gap widened in biology and government. In biology, 72.9 percent of white students passed, compared with 32 percent of black students.

But Hispanic students in St. Mary's recorded strong scores. Hispanic students scored higher than whites, blacks and Asians in all subjects. They had passing rates of 84.6 percent in biology, 86.7 percent in government and 69.6 percent in algebra. Hispanics also improved in all subjects, including an increase of 23.7 percentage points on the government test over last year.

"We are pleased in terms of all the subgroup performances. When we really can get those higher percentages of students passing, [there is] really the possibility of reaching 100 percent passing," Ridgell said.

The Hispanic population in St. Mary's schools is fairly small, so scores can take large swings from year to year. Of the 5,214 students enrolled in high schools last year, 101 were Hispanic, including 15 at Chopticon, 52 at Great Mills and 34 at Leonardtown.

In Calvert County, school officials said the biggest cause for concern is low math scores. One-third of students failed the algebra exam.

"We've clearly got our work cut out for us," said Carol Reid, assistant superintendent for curriculum and instruction. "We've got to be moving faster than we've been moving."

She said the school system is not panicking.

"I can't become overly concerned with any one year's results or any one data point," she said. "I have to be concerned that we're moving in general in the right direction."

School officials are spending a lot of time looking over the math scores, but Reid said exam results should not become the school system's primary focus.

"This isn't about a test. This is about kids who need to be more proficient and more comfortable using math in everyday life and in their careers," she said. "The test is just telling us how well we're doing."

Staff writer Amit R. Paley contributed to this report.