Miriam D. Clark says she has 24 reasons why Fairfax County should revamp its sex education classes: two dozen students who have become pregnant during her four years at Fairfax High School.

Last spring the Fairfax School Board seemingly took the first step toward ending Clark's frustration, directing its staff to consider revising courses so restrictive that teachers are prohibited from answering any impromptu questions from their students.

Nine months later the county remains months away from approving the new courses, a delay that threatens to reopen a controversy that split the county like no other educational issue in recent years.

"I don't think the present program is working," says high school senior Clark, echoing the sentiments of many students in the region's largest school system. "In fact I know it's not working from the number of pregnancies I've seen."

Frustration with the Fairfax sex education program is not limited to students. Gloria Veitlo of Planned Parenthood of Metropolitan Washington accuses the school board of stalling.

"I believe it's a very calculated thing on the part of the board," says Veitl, who says she fears the board is backing away from its commitment to revamp what was generally considered to be the area's most restrictive sex education program.

School officials, who had said that their new courses would be designed by January, deny they are retreating and say they have more passing issues -- such as the school budget -- to consider first. Opponents of expanded sex education courses say they are delighted by the board's inaction.

They have formed a new group, "Fairfax Citizens for a Positive Education," and are attempting to rally parents to resist any program that will allow teachers to discuss the so-called "Big Five" sex topics in the classroom. Under the current program teachers are prohibited from discussing contraception, abortion, masturbation, incest and rape, or taking any unwritten questions from their students.

Under the county's guidelines, which administrators and teachers say virtually all instructors adhere to, lectures are limited to what students describe as boring discussions on reproduction. The voluntary classes are, in fact, so limited that less than 2 percent of the eligible high school students bother to sign up for them.

A few teachers may violate the rules by giving students additional information but they are "few and far in between," says a woman who is involved in counseling suburban youths on birth control. "And those who do will do nothing more than give a student a brochure [on the signs of pregnancy] without saying a word."

Some critics of the county's delays say the seeming indecision over the sex education program is typical of the way the school bureaucracy handles any controversial issue. The extremely cautious nature of the board has become a laughing matter. Precipitous action is "one thing this board has never been accused of," board member Gary Jones once told his colleagues.

Defenders of the school board point out that last spring the board could not approve a revised sex education program because none existed. Thus the board had to ask for a study.

Since then, administrators say they have encountered some unexpected problems. "We've really been involved in staff reorganization [because of a new superintendent] . . . and preparing our budget," says Douglas M. Lapp, the school administrator in charge of the sex education study. Lapp denies that the school staff has been told to delay its reports, but acknowledges that the board "doesn't want to spend the whole spring on it."

School Board Chairman Ann P. Kahn says that even if the new courses had been proposed in January, the board could not have held public hearings on them then because of budget debates.

Last year, the school system conducted a countywide survey and found that 95 percent of those interviewed favored a more liberal sex education course.

But when the subject came up last May, opponents of liberalizing the courses jammed board meetings and gathered 10,000 signatures on a petition urging the board to leave the courses untouched. Nonetheless, the board called for the study.

Teachers who run the current courses and students who take them are nearly unanimous in condemning them as ineffective.

"This is the last year I try to teach sex education," says Anne Heller, who has taught the subject at W. T. Woodson High School for four years. "It's too frustrating. It's frustrating for me and it's frustrating for the students."

Heller says it isn't what she teaches in her class that is frustrating -- it's what she can't teach.

"The biggest problem I see is the misinformation they [students] have," says Heller. "I can't correct them if it borders on one of the [forbidden] topics."

To underscore her anger, Heller has compiled a list of written questions that went unanswered in her classroom. Among them: "Where is the nearest free VD clinic?" "What if you think you are pregnant and can't tell your mom?" "Does a gynecologist ask your real name?" "Is the pill dangerous?" and "Can damage be done to a person who has sex at too young an age?"

Deciding whether teachers can answer any of those questions will be one of the issues the Fairfax School Board will face this spring, a prospect board members say they dread.

"I must say . . . [the earlier sex education debates] were one of the most unpleasant experiences in all my years on the board," said longtime school board member Anthony T. Lane at a recent meeting. "I just wish it would just go away."