She hated her fifth-grade teacher. Decades later she decided to save his life.

This is the story of an earnest English teacher and the precocious 10-year-old who hated him.

It’s about how that girl grew up to pull off several lifetimes’ worth of death-defying feats.

And how, a few weeks ago, she performed the most spectacular one of all.

More than 40 years after Montana Miller left her fifth-grade nemesis behind, she gave him a gift that she hoped would savehis life.

We’ll get to that, but let’s start in 1980, at The Bromfield School in Harvard, where Miller had what she considered the extreme misfortune of getting stuck in Mr. Mitchell Grosky’s reading class.

She bristled at the books Grosky assigned, too silly and slow and easy. Miller’s parents had started the local newspaper, the Harvard Post, and fed her love of reading and writing far beyond her years. Grosky bored her. She constantly challenged him in the classroom.

“I absolutely could not stand him,” said Miller, now 55. “It was a battle of the minds, a battle of wills.”

Her parents asked Grosky to give their daughter more challenging work. Grosky, relatively new to teaching middle school, was less adaptable than he would later become.

“I feel like I was maybe playing a role of what I expected a teacher to be,” Grosky said. “I look back at that time and realize that ‘Boy, I wish those kids could have had the teacher who I became later on.’”

Middle school ended, and Miller was delighted to leave Mr. Grosky behind forever, her frustration with him and his class just a fading memory.

But Grosky would remember something else, not the passion of her dislike, but the brightness of her potential.

“She is,” he said, “maybe the most brilliant, most creative student I’ve ever had in any grade level.”

He would go on to a long career as a teacher and a principal. She continued to excel through high school, smashing the SAT, becoming salutatorian, being accepted to a bunch of prestigious colleges. And then she joined the circus.

OK, so here we get to the second-most improbable part of this story.

“It’s hard for me to tell it without people thinking that I’m lying or just crazy,” Miller said.

For as long as she can remember, Miller has wanted to fly. As a little kid, she had no fear of heights, clambering out an upstairs window to spend hours on the roof of her family’s house in the woods. Some kids live to run faster. Miller lived to get up higher.

She was a competitive gymnast in high school, when somebody suggested she might enjoy the flying trapeze. So at 17, Miller moved to France to attend a renowned circus school and then joined a circus in San Francisco. After a year of that, at 22, she started at Harvard, where she got a degree in folklore and mythology.

She was on the platform diving team in college, but that still wasn’t high enough. In 1996, she competed in a cliff-diving competition in Acapulco. She also worked at amusement parks, diving into pools from 80-foot-high platforms.

“It seemed very exciting and romantic at first, but the reality was, I knew I was going to end up really injured,” she said. “So that was when I decided to apply to grad school.”

At UCLA, she became an expert in adolescent cultures, earning her PhD in folklore and mythology. She started skydiving. Then speed skydiving, which involves hurtling to Earth in free fall, head-first, at 250 miles per hour. She landed a tenure-track position at Bowling Green State University in Ohio, where she’s been teaching for 20 years. She loves mentoring students and leading classes — it’s like performing.

In 2023, at age 53, she took up skeleton racing — jumping onto a sled and hurtling down a twisting ice track, face-first, at 80 miles per hour. It is terrifying, but safer and more fun than jumping from planes.

At this point, you might be wondering whether Miller has some kind of death wish. She gets upset when people suggest that. She is simply driven by a need to make her body do impossible things. And she overcomes very real fear, and sometimes debilitating anxiety, to do it.

“Nobody cherishes life more than me,” she said. “Nobody has a more heightened sense of the fragility of life than I do.”

While Miller was learning to fly, Grosky was trying to become the best teacher, the best person, he could be.

He taught elementary school, then became a principal in Athol, his hometown. He learned how important it was to give every student the exact individual support they needed. He and his wife raised two daughters. He got increasingly involved in his temple, in progressive causes, and in local politics.

“I always told students to run your life so that when you brush your teeth at night and you look in the mirror, you are really proud of the person looking back at you,” said Grosky, now 74. “I’ve always tried to do that for myself as well.”

Around 2012, Facebook brought Miller back into Grosky’s orbit. He was in awe of his former student’s exploits, delighted by all she had achieved academically and aerially. He was also unsurprised, given what he’d seen in her all those years ago.

Miller was intrigued to receive a message from Grosky. She saw that he had become an accomplished landscape and nature photographer, and that he was speaking out about the progressive values she shared. Well, she thought, he’s obviously not a jerk any more.

“So we became friends,” Miller said.

Grosky went to see her at a storytelling event, in which, suspended from a pair of gymnast’s rings, she recounted the tale of a jump in Nicaragua that went horribly wrong. When she was skydiving in Orange, she invited him to take pictures, and they went back to Athol to eat lunch with his family. In that conversation, and in the many that followed, they talked about music and poetry and how the world should be. They discovered they shared the same favorite line from “Les Miserables”: “To love another person is to see the face of God.”

“This person that I had these memories of hating, now I could see all the beauty in him,” she said.

Grosky watched his former student teach a few of her folklore classes via Zoom, fascinated by the lessons and in awe of Miller’s ability to reach kids where they were. He told her so.

“Who knew that all these years later, the approval and love of my former enemy would feel so amazing,” she said. “The way he expresses his pride in me for the person I’ve become, and always was, is healing in some way I can’t explain.”

By then, Grosky was living with kidney disease, and facing the final stage of the illness. Every day, 12 people die waiting for a donor kidney, according to the National Kidney Foundation. He knew there was a good chance he would be one of them.

“In the time I have left,” he told people, “I want to do as much as I can for as many people as I can, for as long as I can.”

He has remained deeply involved in the schools and in local politics, because that is where the most direct change happens. He uses photography and Facebook to share hopeful news from his community, to promote small businesses, to show people there’s some good out in the world. He throws himself into his causes.

Last summer, in a long Facebook post, he told his friends about what he was facing. He received scores of supportive messages, as people offered their prayers and wishes of good luck. Buoyed by their warmth, Grosky was grateful.

Miller was incensed.

Grosky didn’t need good wishes, he needed a kidney. Why weren’t they offering to get tested to donate?

She was sure she was the wrong blood type. Still, mostly to avoid feeling like a hypocrite, she got tested, and discovered she had been mistaken.

“I’m willing to see if I’m an acceptable donor, but I know the requirements can be so strict,” Miller told him, “so I hesitate to get my hopes up.”

“Hesitant to get her hopes up,” Grosky said, still marveling. “She wanted so, so much to do this for me.”

“I wanted to help Mitch so badly that it became almost painful,” she said.

It isn’t easy to become a kidney donor. The tests are invasive and grueling. In the midst of it all, Miller went to see Grosky in Athol, and he was struggling to express how deeply grateful he was.

“Well, Mitch, I’m not just gonna let you die,” Miller said.

In December of last year, Grosky was with his wife, Anne, on a long-planned cruise from Paris to Zurich, one he couldn’t help thinking would be his last.

One night, a message came through from Miller:

“Mitch — WE ARE A MATCH!!!!”

Miller had finally gotten word that she was not only compatible, but the best possible match for him.

Grosky was overcome. “You are one of the most extraordinary, giving, loving people I have ever had the great privilege of knowing,” he wrote back.

“The benefits to me will be similar to the benefits to you,” Miller responded. “A new perspective on life.”

On April 21, Grosky and Miller lay in adjoining surgery rooms at UMass Memorial Medical Center as a team of doctors transferred Miller’s right kidney to her fifth-grade teacher’s body, where it is currently working like a dream.

They are both still in a great deal of pain, Grosky at home in Athol, and Miller in Long Island, N.Y., where she lives with her boyfriend, Mario Maura, a skydiver.

“The pain I’m going through now is definitely not more than I can handle,” Miller said. “It almost feels good, like this pain is something that is a privilege.”

Is it possible to feel more whole by giving a part of yourself away?

Each of these two extraordinary, and extraordinarily thoughtful, people are dealing with complicated emotions.

“I’m feeling this survivor’s guilt,” Grosky said. “I continue to be absolutely astounded and almost perplexed by the fact that someone like Montana would allow some surgeon to cut through layers of skin and muscle, and take out an organ to donate to me. And I often feel very much unworthy of that.”

But this has been a gift for Miller, too. She believes she has failed at many things in her life — that, despite her mind-blowing achievements, she did not reach the heights she’d hoped for with the trapeze, or high diving, or skydiving.

“I didn’t want to tell anybody that this might be happening, because I was pretty sure that this also would end in failure,” she said.

Grosky knows Miller is the only person who could ever see herself as having failed, at anything. He couldn’t wait to tell people who she was, about all of the amazing things she has done, and about how their journey had started all those years ago.

“Awesome has become a slang term,” Grosky said. “But awesome is when you look at the Grand Canyon. Awesome is when you see pictures of the moon. She comes closest to anybody I’ve ever known to really being awesome, in the truest sense of the word.”

The road ahead for Grosky is hard, but he hopes it will be long. He will spend every day honoring Miller’s gift, by being as kind as he can to as many people as he can.

“You don’t know what people are going through,” he said. “You don’t know what private battles they’re waging, either inside their own body or at home or out in the world. And so at the very least, you can simply be kind.”