One of Maisie Kate Miller’s schoolmates always had something belittling to say — about her body, her boyfriend, her fashion choices. But that last little dig, no big deal in itself, brought the 15-year-old sophomore at Marblehead High, north of Boston, to tears a couple of weeks ago. On the stairwell just behind her, the other girl, who’s a sports standout in the school, was loudly riffing on Maisie’s hairstyle: “Who wears pigtails still? What is this, kindergarten?”

“I turned around,” Maisie said, “and she said, ‘Keep walking!’ I don’t know, I was having a hard week anyway, and by the time I got to bio, I was crying.” Maisie’s mom, Joanne Miller, texted her back and advised her to just let the incident go: “Don’t give it any energy is what I told her.”

What came to Maisie, though, was an idea for passive resistance, pigtail-style: Instead of either scurrying away or returning the girl’s nastiness in kind, she’d wear her hair like that all week — I’m fine the way I am, thanks — and maybe get a couple of friends to do likewise. She poured out her heart — and her plan — on Facebook, then headed off to her after-school babysitting job.

When she had her first chance to check in again, a few hours later, she was overwhelmed to find more than 500 notifications and hundreds of friend requests waiting: “Some of them were people I’ve looked up to and never met! I started shaking and couldn’t stop.” But — and this is my favorite part — Maisie did manage to type out a second status update, asking for restraint: “I’d like to remind people that this is a protest against bullying,” she wrote, so bullying the girl right back “would be against the movement,” which she dubbed ‘Pigtails for Peace.’

The next day, much of the school in the historic fishing village — girls, boys, a dog and at least one teacher — was pigtailed, and the bully absent. “There were hundreds of them — almost all of the sophomore class” copying Maisie’s ‘do, said Loren Weston, a counselor and sponsor of an anti-bullying club. “People from every friend group and year did it,” said a junior who didn’t want to be named. “The way she dresses — she’s funky — and outspoken and positive, but she hadn’t been feeling so good,” the girl said, and kids were glad to have the chance to rally around her.

In the days since, the student who’d mocked Maisie has not only backed off but sent a message of contrition through friends: “She’s been going through some stuff, too,” Maisie told me on the phone, and hopes that down the line, they’ll be able to talk about it. She’s also gotten multiple messages along the lines of “She’d been bullying me, too, and now she isn’t any more; thank you!”

Old-fashioned cruelty has always gone on, of course; I’ll never forget the old German nun who routinely yelled at a boy in my class who had trouble reading aloud that he was “so stupid,” — STYOU-pid, she pronounced it — or the girl with albinoism at summer camp who everyone said was a lesbian; I sat with her at lunch one day, not out of compassion, I’m sorry to say, but because she was ahead of me in line in the cafeteria, and that’s how we usually sat. I still remember the stage whispers around us as everyone else steered clear, and have often wondered what became of her, and wished I’d had the moral moxie to get to know her.

A few prep school pranksters and Mean Girls keep their skills up long after graduation, too; when a colleague made fun of the giant crucifix passed down from my grandmother a decade ago — “God, even Madonna doesn’t wear those any more” she said; do these people work from a handbook? — I wanted to cry in middle age.

Cyber-bullying has only upped the ante, making it possible for Dharun Ravi, the Rutgers freshman who set up a webcam to catch his gay roommate making out, to widely disseminate his handiwork in a way that led to Tyler Clementi’s suicide. But here Maisie has shown us that social media can also be the bullhorn that amplifies the word ‘no,’ and stops the intimidation.

It’s important, I think, that it was Maisie who came up with her own way out of the problem. And what she did instinctively is a kind-hearted version of the “shaming” suggested as a way of internally policing a common social area – a school, or an Internet group where the humans involved actually see each other occasionally – by the late Elinor Ostrom, the first woman to win the Nobel Prize for economics.

Maisie is “someone who sticks up for people,” said Weston, the counselor who leads the anti-bullying group in Marblehead, “and that’s why this response.” I found Weston on Facebook, which is where I first saw Maisie’s story, through an acquaintance who’s from Marblehead, and she led me to Maisie and her family.

Her mother thinks that Maisie’s insistence on sticking up for people comes from watching her father, a surgeon who was diagnosed with a brain tumor when she was just three, become more and more compromised in the three more years before he died. A theater kid with flair and “a big personality,” her mom laughs, she’s the sort of person who won’t go to the party if her buddy with Tourette’s isn’t included. The kind of independent spirit who, when told that her saleswoman mom couldn’t swing the Shakespearean summer in England that she’d hoped for, got busy working at various jobs and paid for the trip herself.

Maisie made me laugh right off the bat by prefacing our conversation with, “I want to apologize in advance for the fact that I’m going to say ‘like,’ a lot.” But she’s taught me something serious. Some wise souls are young in age, and this one has reminded me that the majority usually does want to do the right thing, and is maybe only waiting to be invited and shown how.

Melinda Henneberger is a Post political writer and anchors the paper’s She the People blog. Follow her on Twitter at @MelindaDC.