Less than an hour before she found her son''s suicide note, Camilla Barry was laughing with him over lunch.

It was a rare Monday afternoon when Clive Barry, 16, had the day off from Tamalpais High School in Mill Valley, and his mother was home from work to eat and take a nap. Clive talked about how much he respected his father. They made plans to hang out later in the afternoon.

But when Camilla Barry woke up, her son was gone. The note he''d left said he was going to kill himself. An hour later, authorities found his bike at the Golden Gate Bridge. Clive''s body still hasn''t been found, but authorities presume he jumped to his death Jan. 8.

"I''ve come to realize I didn''t know Clive as well as I thought," Camilla Barry said. "His death was a shock to me. There were so many things he didn''t tell me. Not necessarily bad things, just things. He''s a teenager, so we thought he was still in our realm. But I don''t think we knew Clive."

After a teen suicide, family and friends often are left wondering if there were signs they missed, whether they should have seen it coming. Indeed, there are signs, but they can be subtle and difficult to spot -- especially for parents and friends who don''t know what to look for, or who don''t want to admit that a child is depressed.

Clinical psychologist and author Madeline Levine, who has been in practice in Marin County for 25 years, said she increasingly sees teens who are stressed, depressed and still flying under the radar because they look good on the outside.

"There is a kind of kid now with this relentless kind of perfection," said Levine, who recently wrote "The Price of Privilege: How Parental Pressure and Material Advantage Are Creating a Generation of Disconnected and Unhappy Kids."

Some teenagers do exhibit classic signs. They start falling behind at school, grow uninterested in activities they used to love, have trouble sleeping, turn to alcohol and drugs. But those signs don''t always manifest themselves in time.

"I believe some of the typical signs of depression -- the checklist from the pediatrician -- are not always evident in a child," said Anne Magill, whose daughter Grace, a student at St. Ignatius College Preparatory in San Francisco, took her life in 2005.

Magill said her daughter was gorgeous and spirited and never missed a day of school but started cutting herself in September 2005. A friend recognized her cry for help, and her school and family quickly got mental health professionals involved. Even so, she died a suicide months later.

And many teenagers make a concerted effort to hide their pain.

Camilla Barry found a book in her son''s room with a chapter on how to hide feelings and keep secrets.

"I''m mad he didn''t let us know what was going on," she said. "But he planned it that way."

In fact, he''d tried to kill himself at age 14 by swallowing rat poison. Afterward, he went to a counselor but hated it -- his mother didn''t like the therapist either -- and he stopped going.

Clive''s was the third suicide in four years involving current or former students at Tamalpais High. That''s not an unusual number for one community. In fact, suicide is the third-leading cause of death among people ages 15 to 24, according to the federal Centers for Disease Control and Prevention.

Nationwide, the suicide rate among teenagers has fallen since 1990, from 11.1 per 100,000 15- to 19-year-olds to 7.3 per 100,000 in 2003, the most recent year for which consistent national data are available. There were 1,486 teen suicides in 2003.

Teenage boys are more likely than girls to kill themselves, with a rate of 11.6 deaths per 100,000 in 2003, compared with 2.7 for girls, federal statistics show. The suicide rate for people of all ages was 10.8 in 2003.

Among people ages 15-24, which is how statistics are broken down by ethnicity, those most likely to take their own lives in 2003 were Native American males, at 27.2 per 100,000. White, non-Hispanic males in that age group had the next-highest rate, 18.2 per 100,000, though white males in all the older age groups had higher rates.

Women of all ages and ethnicities had lower rates than men, and their overall rate was 4.2 per 100,000. The lowest rate for males was 8.3 per 100,000, for black men ages 65-74.

Occasionally, a cluster of suicides will rattle a community. In fall 2004, Clayton Valley High School in central Contra Costa County was rocked by two suicides and one attempted suicide of students or former students -- all in a three-week period. When a fourth student at nearby College Park High School killed herself, less than a month after the first suicide, rumors and parent paranoia about suicide pacts sent the community reeling.

Retired Clayton Valley High Principal John Neary said schools have to face the problem of suicide head-on, without glorifying it.

"Just the facts," he said. "What kids eat up is the drama of it all."

He also urged parents to "be parents."

"Parents these days don''t hear the cries for attention, for support, for direction," Neary said. "They are too busy today, making a living, doing other things. There are so many divorces."

Schools are seeking new ways to deal directly with the threat of suicide. Three private schools in San Francisco, including St. Ignatius, are trying a program called TeenScreen developed at Columbia University to identify students in trouble. The program includes a questionnaire for ninth-graders about whether they have been depressed, have a problem with alcohol and drugs or have tried to kill themselves.

Teens who score high are interviewed by counselors. If they are at risk, TeenScreen contacts their parents and makes referrals for further counseling. The 20-minute test is voluntary and requires parental consent.

"We''ve been amazed by how open kids are about what''s going on with their lives. They are more likely to be forthcoming on pen and paper or with a computer questionnaire than face to face," said Dr. Susan Smiga, director of the Children''s Center at Langley Porter at UCSF, which runs TeenScreen in San Francisco.

TeenScreen is being used at more than 400 sites in 43 states, said Executive Director Laurie Flynn in New York. About 30 percent of San Francisco private school teens tested so far were found to be at risk, Smiga said, and about half of those were referred for treatment.

Local public schools have resisted TeenScreen. San Francisco Unified School District, for example, passed on TeenScreen because it can generate false positives and drain counseling resources, said spokeswoman Gentle Blythe.

Other critics worry TeenScreen could send kids unnecessarily into treatment and land too many on psychiatric drugs. And some critics say parents should be in charge of those lessons for their children.

Some communities are addressing suicide prevention with more traditional methods.

Youth pastors with Celebration Christian Center in Livermore, where Livermore High has lost two students to suicide in two years, formed the nonprofit Youth United to tackle the problem.

Last week, Youth United arranged for motivational speaker Michael Miller to talk to the student body, and next week counselors will visit classrooms to start conversations about how to identify if a friend needs help and how to ask for help. Youth United also hopes to open a crisis hot line in the near future, said Pastor Aaron Chidester.

The school, which also lost a student each year from 1998 to 2000, has introduced several other programs over the years to head off suicide, said Chandra Whetzel, a school secretary whose son Ryan, a graduate, killed himself in the family garage when he was 19 in 1998.

Whetzel, like many parents, was taken by surprise. She knew he had been caught in an insurance scam and was worried, but she didn''t know he was desperate.

"Kids today only tell the parents what they want to hear. I think my son felt that he let us down," she said.

After Ryan died, she and her husband introduced a program at Livermore High in which the school''s 2,000 students each receive cards bearing hot line numbers and yellow ribbons at the beginning of the school year.

Magill is working through the Edgewood Center in San Francisco -- which provides child counseling and other services -- to educate students, eliminate the stigma of adolescent mental illness and help peers recognize the signs that a friend might need help.

And Camilla Barry is talking.

Clive wasn''t, she said, a troubled kid. He didn''t seem to display any of the obvious signs of distress. He had a wide group of friends and a girlfriend. He wasn''t a stellar student, but he was active at school. He was cheerful at home and liked to spend lots of time with his family.

He seemed fine after he quit seeing the therapist two years ago, she said. But in hindsight, she wonders if he ever got over what was troubling him. He had been going through a tough time at school -- something she says now was probably worse than she knew.

"I''m sort of horrified that we did not take that (first suicide attempt) more seriously," Camilla Barry said. "He told us it was nothing, and I just believed him. Clive had this way of seeming very grown-up. And when he told me, ''Mom, it''s done, it''s over,'' I just believed him. I shouldn''t have believed him.

"But he was so young when he did it," she said. "And he seemed happy. There really weren''t any other signs. It''s only in retrospect, little comments he''d make. He was probably thinking about this for two years."