Prince George's County school officials said yesterday that only 8 percent of the more than 14,000 high school students recently declared ineligible for extracurricular activities because they failed to earn a C average were actually participating in such activities.

The C average requirement that was implemented this winter affected a total of 1,187 students: 19 percent, or 337, of the 1,743 students participating in winter sports and about 11 percent, or 850, of the 7,427 students in nonathletic activities. Nineteen percent, or 338, of the 1,767 students in student government were declared ineligible.

"The data show that the effect of the eligibility rule not only cut across all activities but also identified as many student government members as it did athletes who did not qualify," said Brian J. Porter, the school spokesman.

Early in February, school officials announced that more than 39 percent (more than 14,000) of the 36,197 students in the ninth through 12th grades were ineligible for outside activities, a figure that shocked school officials. The figures released yesterday indicated that a much smaller number actually lost membership on teams or clubs.

Of the 9,170 students in such activities, 13 percent, or 1,187, lost such membership.

The C average rule continues to draw strong reaction from the public, particularly from those who believe that student government members should be exempt. About a dozen students, parents and teachers urged the Board of Education last night to rescind the rule or exclude student government.

"If you only let average or above-average students participate in student government, what kind of representative government do you have," said Anne Terrier, student government president at Laurel High School. She said she earned about a B-minus average.

Ben Howard, who was removed as Laurel High sophomore class president because he did not receive a C average, said including student government in the rule "is like requiring the president of the United States to pass a test to stay in or get in office."

Although some students and parents have charged that including student government under the rule conflicts with a state policy, board attorney Paul Nussbaum has issued an opinion declaring the rule legal.