WASHINGTON -- The grades of high school graduates keep climbing, reaching a B average in the latest count, but far less certain are gains in achievement.

High school seniors in 2000 finished with a cumulative grade point average of 2.94 out of four possible points, with four equaling an A on the scale schools use, a study shows. A decade earlier, the typical grade point average was 2.68. It rose throughout the 1990s.

That trend comes with other positive news. More students are taking the rigorous math and science courses demanded by colleges and employers, according to the Education Department's sample of 21,000 student transcripts in public and private schools.

From boys to girls, whites to blacks, East to West and in all four high school years, grades were up everywhere. But the study and the officials who presented it Wednesday did not draw firm conclusions about whether those higher marks reflected higher learning or grade inflation. Other achievement measures during the same period, for example, showed less rosy results.

Reading scores stayed flat through the 1990s, according to the federal test that tracks trends among 17-year-olds. Math and science scores leveled out after 1992.

A different federal test for high school seniors showed dropping math and science scores in 2000. Gains in the SAT and ACT college admissions tests did not match the rise of high school grades.

The study also found that students with higher grade averages did better on the national math and science tests.

"My experience tells me that the increase in GPA is probably a reflection of what our students know and are able to do, but it's difficult to be certain because of the way grading is done," said Katy Harvey, principal at Bethesda-Chevy Chase High School in Maryland.

States and schools have worked to match up their courses with state standards, trying to ensure that those who do well in class will do the same on tests. But grading comparisons can be tricky.

Algebra I may be an extremely different course from one district to the next. Also, school systems vary widely in their range of offerings and teacher training.

Then there is the grading pressure on teachers. Ilyssa Rothman, a teacher at Harvey's school, says it comes from all sides: administrators who want a set number of high grades, parents who want to see good report cards and students fighting to impress colleges.

"They will come up and say, 'Oh, I have an 88.9. Can I have an A?" Rothman said of students. Her response: "No. You earned the 88. Work harder next quarter."

Over the past 10 years, colleges have placed less weight on grade point averages, said David Hawkins, public policy director for the National Association for College Admission Counseling. It ranks third on their list of priorities, behind the strength of students' curriculum and scores on standardized college admissions tests, Hawkins said.

"I think there is some grade inflation because you've seen the behavior of college admissions officers trying to correct for that," he said. "But the percentage of graduates moving on to college, and enrollment in postsecondary education, have also gone up ... You do have more qualified students getting into college. So the truth is somewhere in between," Hawkins said.

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On the Net:

High School Transcript Study: http://nces.ed.gov/pubs2004/2004455.pdf