Two 15-year-old Fairfax County boys, described as best friends, committed suicide within eight days of each other, sending shock and grief through Robinson Secondary School and causing county officials to dispatch crisis teams to the huge school.

One youth apparently hanged himself from a tree in the family yard Sept. 25; his body was discovered the next day. On Thursday, five days after the first youth's funeral, the second youth hanged himself in a utility shed at home.

In an effort to calm the boys' shaken classmates, school officials brought teams of counselors into the building off Braddock Road this week to hold open-door meetings with students. Teachers were counseled at a meeting Monday on how to help students and a session with parents was held last night.

The double suicides, the first among school-age children in the county this academic year, focused new attention on Fairfax County's school suicide prevention program, which was praised at a U.S. Senate hearing last year as a national model. The program to train teachers in suicide prevention began four years ago, prompted by the suicides of 11 young people during the 1980-81 school year.

County officials believe the program helped lower the number of school-age suicides to five last year, at a time when the number of teen suicides was rising nationally.

"Relatively speaking, we feel we have addressed the issue," said Beatrice Cameron, an assistant superintendent for the county. "It's a tragic event."

The first boy's suicide was announced over the school public address system Monday, and students were encouraged to stop by for informal counseling sessions, skipping class if they felt it necessary, according to Dolores Bohen, a Fairfax County school spokesman. The second boy's death was announced yesterday at a faculty meeting; teachers then told students in class.

"It was devastating to the students," said Rebecca L. Perry, president of the school PTA.

The school corridors and locker rooms, usually bustling and noisy with the school's more than 4,000 students between classes, were eerily silent, said seventh grade history teacher Richard Davala. Some students -- boys and girls -- cried openly.

Both youths had received professional counseling, said Myra Herbert, who heads the suicide prevention program as coordinator of School Social Work Services. One boy's friends told counselors they had noticed he had isolated himself socially in the days before he killed himself.

Herbert said isolation is a common sign, but that it is also common for youths who have decided to commit suicide to be in a very good mood, because their depression lifts once they have made a plan.

Herbert said school officials will decide next week on an appropriate memorial to the two boys. "Kids feel less powerless if they can do something," she said.

Perry said the school PTA hopes to have a suicide prevention program for parents.

Counselors are telling the upset students to air their grief and "tell people when they need help," Herbert said.

She said they are being urged to tell an adult when they notice a friend in trouble. "It can be the friendliest kind of thing you can do," she said.

Her message to parents in counseling sessions: "Listen to your kids. Most of all, listen. Ask them about their feelings."

"Fifteen is an impulsive age," Herbert said. "Taking their grief seriously is very important. But it's also very important to understand that sometimes group feelings can run very strong."

She also urged parents not to leave children alone if they are worried about them, to steer them away from the depressants of drugs and drink, and to remove guns and lethal medication if there is cause for concern.

Grief-stricken children should be allowed to attend memorial services if they wish, to help resolve their feelings, she said.

Experts say the warning signs of a potential suicide in school-age youths often include difficulty coping with such factors as divorced parents, a learning disability, academic pressure or frequent family moves.