Fairfax County students are confused, bothered and bewildered about their grades.

This year, in an effort to guarantee that an Am one Fairfax school means the same as an Am another county school, the school administration is enforcing its long-established grading scale.

Some students are surprised to find, for example, that the 91 points they earn on a test this fall gives them a B, when the same score last year earned them an A.

"It has a lot of students very upset," said Lynn Taylor, a Robinson High School senior and a member of the countywide Student Advisory Council (SAC). "It especially hurts the average students who thought they had solid Csand now are finding they're getting Ds."

Under the grading scale, a score of 94 to 100 equals an A, 93 to 87 equals a B, 86 to 80 equals a C and 79 to 70 equals a D. Scores below 70 equal an F.

The tightened enforcement is an effort to standardize grades in intermediate and high schools across the 400-square-mile county and to ensure high academic standards, school officials say.

Many parents, principals and teachers had complained that letter grades for equal numerical scores varied from school to school; and sometimes from class to class, since the current grading scale was set in 1963.

At the same time, parents across the nation have been calling for higher academic standards, Today's educational atmosphere, educators say, rejects the "social" promotion and graduation practices of the 1960s when grades were credited with less importance as a measure of a student's success.

"Now, in the '70s, who wants to turn out students who can't read and white?" asked Nancy Kokus, a Fairfax teacher who was chairman of a special task force that developed a new handbook this year "reaffirming" the grading policies for grades seven through 12. Grading policies in the elementary grades were tightened last year, said William J. Burkholder, associate superintendent for Fairfax schools.

Kokus, who with other school officials explained the grading scale to individual faculties before classes began last month, said in the 15 years since the present grading policy was established, many schools and individual teachers had considerably "loosened the interpretation of the scale," with some giving As for scores of 90 and above, Bs for scores of 80 and above and Cs for scores of 70 and above. "We're hearing a lot of complaints; we hear it every time we give a test back (to the students)," said a teacher at the new South Lakes High School in Reston. "We should toughen up a little, but I can see the students' side, too."

Some students say the scale is too tough. Others cite different problems, such as the possibility that Fairfax graduates may be at a disadvantage in entering college when compared with students from areas where the grading scales may be more lenient.

Taylor pointed out that many Fairfax high school students take "advanced placement" courses that are considered college level and that the tight grading scale may be unfair to them since they already are studying more advanced material.

"I'm the type of student who always strives for an A," said Taylor, who takes advanced-placement courses in English and history. "It makes me pretty sad to think that this year I'm probably going to make Bs in course where I used to get As."

She said soem SAC members are considering that the organization suggest to the school board that the requirements for entering school honor societies be lowered to compensate for the tightened grading scale.

Meanwhile, Langley High School senior Chirs Lehman, president of SAC, said he thinks Langley teachers in general have stuck to the grading scale and thus the tougher system wide enforcement has made little difference at Langley.

But Taylor said she believes more Robinson students than usual are receiving the warning notices that lets them know their grades may be falling below a C level.

The grading scale appears to be only one element in the county effort to toughen academic standards. Fairfax students, beginning with this year's 10th graders, will be required to pass "minimum competency" tests in order to graduate. The tests measure a student's "survival skills," such as balancing checkbooks and understanding job applications. Most students are not expected to have difficulty with the tests.

In addition, Superintendent S. John Davis last year required all high school students to complete four error-free compositions in English, and ordered that certain essays in history also be graded by an English teacher for writing standards.

"I think the requirements are getting stiffer. Teachers seem to have less leniency in how they're going to grade, although they call still do things like giving more chances for extra credit and other stuff." Taylor said. "Maybe it won't be so hard for younger students coming up, but students now are really having a hard time."