Judy Sloan's son was a freshman at James Madison High School in Fairfax County when he started talking about killing himself.

"I was scared stiff," Sloan said last week of her 1981 trauma. "I thought that only happened to the scum of society. I felt a lot of guilt and frustration."

Sloan was one of many parents going through that emotional turmoil.

Though her son did not commit suicide, during that same school year 11 teen-agers in Fairfax County did, according to school officials.

Counting the number of students who took their lives during school vacations and the suspected suicides that are recorded as accidental because of family wishes, the actual number for the 1980-81 school year is believed to be more than 20, according to Myra Herbert, coordinator of Fairfax County School Social Work Services.

"I thought I was all alone," said Sloan, whose son spent 15 weeks in a drug rehabilitation center and has since overcome his suicidal dependency on drugs and alcohol.

"If Fairfax had the program they do now, I would have been better prepared to deal with it," she said. "I got my knowledge the hard way."

The Fairfax County Schools began a suicide prevention program three years ago in response to a rash of student suicides in the county and the tripling of teen-age suicides nationally in the last 25 years.

Last week, the Fairfax program was called "a model for the nation" at a Senate Judiciary Committee hearing investigating teen-age suicides.

Nationally, the overall suicide rate has remained the same for decades, but the number of teen-agers killing themselves has increased dramatically, most noticeably in affluent suburbs, according to the National Institute of Mental Health.

Government statistics show that 5,200 adolescents killed themselves last year, but Dr. Susan Blumenthal, the chief of the suicide research unit at the institute, says the actual figure probably is around 15,000.

Many deaths listed as "accidents," she said, were teen-agers who smashed their cars headlong into trees or killed themselves in some other way.

"There is now enough attention on it that we may be able to target some money to stimulate every school district in the country to establish a program like the one in Fairfax," Sen. Arlen Specter (R-Pa.), said last week after chairing the Senate Judiciary hearing.

Fairfax County is the only school system in the area that trains teachers in suicide prevention. Volunteer mental health professionals train every high school and intermediate school teacher in the causes and symptoms of suicide.

All school psychologists, social workers and counselors are trained to deal with potential suicide victims and are prepared to refer students to the appropriate public or private mental health professionals.

In addition to training educators, the program invites parents to attend special PTA meetings with mental health professionals to discuss adolescents' stress-related problems.

Because volunteers are used, the program did not require a budget increase, Herbert said.

Since the program began, the number of suicides in Fairfax has dropped from about 20 to three last year, according to the county's figures.

The Fairfax County program is being expanded this year to include what is called a "student stress program" because of the stigma still attached to the word "suicide."

Teachers identify students who appear to have difficulty coping with one or more of the factors common to many suicide victims: divorced parents, a learning disability, intense academic pressure, a history of moving to many different cities. The students then attend seminars led by school counselors.

One of the students who participated in the pilot for the program last year was Jennifer Bacon, 17. She had moved to five different schools in six years. She was in Hawaii when she learned that she would be spending her senior year among 5,000 new faces in Fairfax's Robinson High School because her father, a naval officer, was being transferred once again.

"I always got the feeling that nobody knew me and nobody wanted to know me," she said softly to the student body in a program that was videotaped by the school last year. "The hardest part was eating lunch that first day and not knowing anybody . . . just a little thing like that brought a lot of tears."

Bacon, now a freshman at Dartmouth College, said last week that she now recommends the program to anyone "who feels like they can't handle something." Talking to others, she said, helped her realize that it was normal to feel extra pressure.

Norman Bradford, the principal of James Madison High School, said he believes that academic pressure is a source of stress that is increasing for teen-agers. This year, for example, Virginia will issue a special advanced diploma for students who take 22 courses.

"Parents are subtly applying pressure to the kids," Bradford said. "Some of the kids think they are not living up to their parents expectations. I hear them. They sit in that chair and say, 'Help me. I'm sinking.' "

Bradford said he has seen a "dramatic response" from students since they began educating teachers and students on suicide.

Madison guidance counselor Sandra Roeder said that students approach her in the office, in the cafeteria, or on her way to her car in the parking lot. They begin talking, sometimes saying they have a friend who they are worried about.

They speak of not being able to shake that "down" feeling since they lost their mother or their best friend. Some talk about dying.

Schools, Roeder said, are the last line of defense for many of these students because "so often at home there is a breakdown of communication."

Schools in Alexandria, Arlington, and Prince George's and Prince William counties have begun to educate counselors in detecting and dealing with suicide, but only Prince William includes teachers in its program.

It is the teachers, said Bradford, who are the critical link between the students and professional help.

A counselor in his school could not possibly know what is weighing on the mind of each of the 1,923 students at James Madison, he said.

But teachers, who deal with students regularly and in smaller numbers, he pointed out, are much more likely to pick up signs of mental stress.

Maggie Birch, a health teacher at Madison High for 26 years, said that the suicide prevention seminars she has attended have been "tremendously helpful."

Previously, teachers had no particular training in suicide prevention, she said.

Birch said that she referred a student for treatment last year after noticing that the student was withdrawing from those around her and changing moods rapidly, two signs of depression Birch had been instructed to watch for.

With the incidence of teen-age suicide so high, she would "rather overreact, than not act at all," she said.

"If we can keep them talking, we know what's on those little minds. It's when they're quiet that I worry," said Birch. "Some of these kids think they are going to teach their parents a lesson. They don't realize how final death is."