Three Annandale High School seniors have committed suicide since classes began last month, prompting school officials to convene assemblies yesterday with the entire junior and senior classes to discuss the tragedies.

At the seniors' meeting, dozens of students stood up one by one and spoke about their problems or offered support to troubled classmates, according to Principal Raymond Watson and several students who were there. Some of the seniors related memories of their dead friends, and others decried their decisions to commit suicide. The assembly lasted 2 1/2 hours.

"It was very moving, very cathartic, very emotional," Watson said.

Similar assemblies are planned with the freshman and sophomore classes at the Fairfax County school today; a meeting with parents of its 2,300 students is scheduled for next Tuesday night, and additional crisis counselors are scheduled to be in the building through the end of the week.

"It's devastating," Watson said of the effect of the three deaths. "The students' reaction is profound, mixed from the kind of grief that comes from knowing someone well to a sense of vulnerability."

The three suicides of male seniors at the school, the last of whom died early Monday of a gunshot wound, are the only ones so far this school year in the county schools, according to spokeswoman Dolores Bohen.

The school system, with 131,000 students, generally has no more than half a dozen suicides a year.

In addition to the suicides of Eric Ragland on Sept. 17, Shane Benson on Sept. 30 and William Wakefield Monday, officials said the death of another senior in an automobile accident this summer and the accidental carbon monoxide death of a former student early last month left students shaken.

Faculty and counselors at the school "are feeling a sense of fatigue, for lack of a better term," Watson said. "We go into action, but behind our action is the fear that we're not doing enough."

School officials said that the three youths who died recently did not know each other well, and their suicides apparently were not related. The school assemblies were being held because the numbers and timing of the tragedies made school officials feel that standard measures -- crisis counseling, public address system announcements, letters home -- were not enough and that a face-to-face discussion was needed.

Watson excused all 650 seniors from class yesterday morning and called them to the auditorium, where he delivered what he later described as a "very direct message" against suicide. The school's guidance director told students about steps that school officials are taking, which include a panel discussion on suicide with student counselors in December.

The school has been under some stress this year because the entire senior class of nearby Jefferson High School, including two of the recent suicides, moved to Annandale this fall when Jefferson closed. Some students said later the meeting helped pull them closer. "Everyone had just the warmest feeling," one senior said.

"Everyone's looking out for everyone right now," said a senior who ran out of the auditorium overcome with emotion. "A girl I'd never seen before in my life came up to me. She wanted to help me. She wanted to make sure I was okay," the senior said.

In the afternoon, Watson called an assembly of the junior class.

"The school is just stunned," said Myra R. Herbert, coordinator of the school system's suicide prevention program, which has trained thousands of county school employes. "At this point, they don't know what to think. They're somewhat immobilized by the shock of it. Kids think death is something that happens to old people. To have it in such numbers among their own collegial group is quite hard."

Herbert urged troubled students to seek help from counselors or teachers at their schools, and she said Fairfax County has 24-hour emergency help available at the Woodburn Mental Health Center in Annandale.

Parents and friends should be alert to changes in a teen-ager that could signal suicide, and should take them seriously, said Ralph Wittenberg, a psychiatrist who is chairman of the Washington Psychiatric Society's public information committee.

Among the danger signs are "fairly striking" changes in personality, abuse of alcohol or drugs, a drop in grades, or physical complaints from previously healthy youngsters, he said.

Another warning sign is a teen-ager beginning to talk about death in terms such as, "I think I'm going to be dead next week," or "I don't want to go on living," Wittenberg said.

"It sounds overdramatic, but it's not something you want to dismiss," he said. Parents or friends should tell the teen-ager they are aware there is something wrong, and should try to get help, Wittenberg said.

School officials did not give reasons for the students' deaths and experts caution about trying to attribute suicide to a particular motive. Outsiders rarely know what goes on under the surface, they say.

However, friends of the third teen-ager who committed suicide said they were particularly surprised at Billy Wakefield's death.

After Ragland committed suicide, Wakefield told friends he would be devastated if any of them committed suicide, according to friends who have known him since kindergarten.

"He was really against suicide," said Jason Reagan. "A week ago, he said he would never commit suicide. Never."

Added another friend, Matt Zeigler: "He said it was a bad way to get out of a problem."