The Prince George's County Board of Education was urged last night to rescind its new regulation requiring students participating in extracurricular activities to maintain a C average. Three fathers, supported by a group of high school students, said the rule is unfair and prevents students from learning valuable lessons through clubs and teams.

"I've seen communication skills and confidence built through writing and presenting speeches for student offices," said William Rodgers of Bowie. "I've seen organization and journalism skills developed putting the school newspaper together. There are no grades for these activities . . . but I assure you the learning is deep, rich and unforgettable."

More than 39 percent of the county's high school students were declared ineligible for extracurricular activities last week because they failed to meet the C average requirement during the fall semester. The rule, which was adopted by the board and went into effect this winter, affected 14,195 of the 36,197 students in grades nine through 12.

Prince George's is among the first school districts in the nation to adopt minimum grade requirements for participation in outside activities. Alexandria adopted a similar rule for athletes, which will go into effect next fall.

School officials maintain their support for the rule despite the high numbers it has affected. "The basic question is is it play time or class time," said Brian J. Porter, school spokesman. "We understand these parents' concern but students need a standard to aspire to and go beyond. We see the C average as the minimum level students should achieve before they participate in after-school activities."

Rodgers, whose daughter Cathy is vice president of the Bowie High School Student Council and received a 2.7 average, cited a "bill of student rights," which says students cannot be denied the right to participate in activities because of grades, except under certain circumstances in sports and performance groups.

Among those who have protested is a group of student government members and advisers who feel student government should be treated differently from other activities.

"I'm glad it applies to athletics," said Hope Butler, president of the county's regional student government. But, she added, "in student government you're elected. These people put their trust in you to lead your class."

Board Chairman Angelo Castelli said the board is reviewing whether student government members should be treated differently and whether the rule conflicts with the student bill of rights.

Mark Fowler, whose son Mark was kicked off the Frederick Douglass High School wrestling team last week because of his grades, also complained. The student who loses membership is a double loser, he said: "He loses in school and he loses in sports and music."

Arthur Curry, who is employed by the schools as a specialist with disruptive students, asked the board to phase the rule in over a year and extend it through seventh grade. He complained that the schools often fail to help students by supplying progress reports or calling parents. Nevertheless, he said, "we're still asking the kids to maintain the average."