CADILLAC, Mich. – Tom Harrison isn’t an expert on bullying.

“I’m just a dad,” he says, as he paces back and forth in school gymnasiums, telling students and teachers about his son, whose life ended in suicide last year.

What he can show them, with the help of a slide show, is a bit about Alex Harrison, the quiet, brainy teenager who died at age 16.

What he can tell them is how Alex endured harassment at school, often with few people knowing because his son rarely told anyone, even his parents.

It is a story that resonates with students, especially when news of bullying-related suicide has become more common. In one high-profile case in Massachusetts, several students have been charged in the death of a 15-year-old Irish girl, who killed herself in January.

“Who in this room has ever been bullied?” Harrison recently asked a group of students at Holton High, northwest of Grand Rapids. About half the students raised their hands.

“Who knows someone who’s been bullied?” he asked. Almost everyone raised a hand.

It’s the kind of response that has driven Alex Harrison’s parents to take their private anguish public. His parents want people to know Alex’s story so they feel compelled to stand up for others like him. “Do it for me,” Harrison implores his audiences. “Do it for Alex.”

CHANGE IN CULTURE

On its surface, Cadillac, Mich., is the picture of serenity, a community of about 10,000 in Michigan’s northwest lower peninsula.

But here and in school districts across the country, officials see a troubling change in student culture. These days, they say, it’s more common for popular kids, good students and athletes to use bullying to jockey for social position. Often, this culture of meanness is amplified by text messages and social networking.

“There really is a dramatic difference in the way students treat one another,” says Paul Liabenow, superintendent of Cadillac Area Public Schools.

He knew Alex Harrison from the time he was a primary school student and remembers him as a quirky, likable kid who was “extremely brilliant.”

At that age, his parents say Alex was already studying college-level anatomy. age 13, he’d built his own computer, using a book to guide him.

That was about the time his parents got an inkling that their son was being teased. He came home from junior high one day and announced, “I found out it’s not cool to be smart.”

In high school, his parents knew that a player on his tennis team was giving Alex a hard time, calling him names and forcing him off the practice court. The coach had dealt with it, and they thought that was it.

In fact, in the months before his death, many observed that Alex was coming out of his shell. He’d just gotten his driver’s license. He had a girlfriend and a core group of friends. A longtime Boy Scout, he was also on the ski team.

Alex was still intensely private and socially awkward, his parents say. Nor did he give voice to whatever was bothering him.

A MOTHER’S SCREAMS

Harold Falan, a Michigan State Police trooper, was one of the first to arrive at the Harrison home on the morning of Feb. 7, 2009, when Alex took his life. As Falan got out of his car, he heard P.K. Harrison’s tortured screams and ran through knee-deep snow into the woods behind their house.

“I’ve never heard a mother scream like that,” Falan said. “It’s one of those things you never forget.”

He found Alex’s mother in the woods, clinging to the body of her only child. Nearby was a shotgun that he and his dad were supposed to have taken skeet shooting that morning. His mom remembers looking at the braces he would’ve soon gotten off his teeth and thinking, “He’s still just a baby.”

There also was a notebook that Alex had taken into the woods to scribble a few notes to his parents. He told them he loved them and that he was very sorry. “But I can’t take it anymore.”

Falan talked with students and teachers, whose stories added up to a conclusion that even his own parents didn’t know: Alex had been harassed and ostracized at school, mostly by a small group of students.

• Falan’s report detailed a lunchroom incident the day before their son died. Alex approached a table of popular students, and one girl used an expletive to tell him to go away, adding, “Don’t you know everyone hates you?”

• A group of students taunted him in a secluded hallway. Some frequently chanted “Creeper, Creeper,” a nickname they’d given him.

• Another student spread a rumor that Alex was looking in her windows at night, which his parents insist wasn’t true.

Though no criminal charges were filed, Liabenow, the Cadillac superintendent, responded by heightening efforts to combat bullying. Teachers and students now attend anti-bullying workshops. More cameras have been added to school hallways. Staff members who monitor those hallways, and the lunchroom, are on “high alert.”

Since Alex’s death, the Harrisons have received e-mails and Facebook messages from parents in the school district who’ve said their children are being harassed, too. Liabenow has vowed that each one of those claims will be investigated by his staff.

“We can’t avoid having these conversations because the kids are talking about it, anyway,” says Ann Cardon, superintendent of Holton Public Schools, where Alex’s dad spoke this month. She has made a promise to students who are bullied or witness it: “If you go to an adult, something will happen. That’s our commitment to you.”

In the meantime, the Harrisons have placed a memorial, a large boulder with a plaque on it and a park bench, next to the lake that borders the high school and junior high campuses.

Sydney Maresh, a good friend of Alex’s, wipes away tears as she sits on that bench and talks about him. He’d be surprised at the response to his death, she says, recalling the long line at his wake that stretched out the building and down the sidewalk.

“Everyone says, ‘If only he’d known how much he mattered to so many people,”‘ says Maresh, a 17-year-old junior.

She spoke about losing Alex at her school’s recent Challenge Day, a workshop used by schools across the country to encourage unity and respect. It was an impressive moment of togetherness, she says — one that she hopes will endure at her school.

“Now,” she says, “it’s up to us.”