Sarah Carr, author of “Hope Against Hope,” directs the Teacher Project, an education reporting fellowship at Columbia Graduate School of Journalism.

From classrooms to boardrooms, playing fields to parenting blogs, “grit” is the buzzword of the moment. Success, the theory goes, has as much to do with character — in particular, passion and perseverance, or grit — as it does with intellect. One of the prime movers of this idea is Angela Duckworth, a professor of psychology at the University of Pennsylvania.

Duckworth was teaching seventh-grade math in the ’90s when she noticed that her most successful students weren’t necessarily the smartest ones but the ones who had endurance and drive. Since then, through her research, and in numerous speeches and articles, Duckworth has helped popularize the idea. She has even developed a Grit Scale, which asks people to rate themselves on such statements as: “I finish whatever I begin” and “I have overcome setbacks to conquer an important challenge.”

In her book “Grit: The Power and Passion of Perseverance,” Duckworth expounds on the concept, staking a claim for the supreme importance of grit over talent. “I have the scientific evidence to prove my point,” she writes. “What’s more, I know that grit is mutable, not fixed, and I have insights from research about how to grow it.”

"Grit: The Power of Passion and Perseverance" by Angela Duckworth (Scribner)

She goes on to detail the habits of the grittiest among us: interest in a pursuit, a willingness to practice, a sense of purpose and a hopeful spirit. When it comes to raising gritty children, she encourages parents to follow the “Hard Thing Rule”: Everyone in the family must self-select one difficult thing to practice — piano, ballet, swimming, French — and persist at least until a natural stopping point arrives, like the end of a sports season.

The book is heavy on anecdote. There is some science: For example, in 2011, an analysis of more than 200 education programs found that teaching social and emotional skills significantly improved students’ academic achievement. Duckworth also describes a few of her own studies. An analysis of West Point cadets, for instance, concluded that their scores on her Grit Scale were better predictors of whether they would make it through boot camp than “Whole Candidate Scores,” ratings that encompass their physical, academic and intellectual prowess.

But “Grit” focuses much more on seemingly endless accounts of world-class swimmers, football coaches, journalists, novelists, artists, spelling-bee champions and CEOs — all of whom testify to the preeminent role that grit has played in their lives. We learn, for instance, how Bill McNabb, chief executive of the mutual fund provider Vanguard, acquired grit as a member of the crew team in college — the first activity he’d tried that didn’t come easily and that forced him to rely far more on hard work than innate talent. “But I kept going,” he told Duckworth. “And then eventually I started getting better.” For McNabb, this experience proved inspirational through his career, a reminder to continue to work hard even in the face of professional setbacks.

The book is readable if repetitive — written in a conversational tone that amply incorporates anecdotes from Duckworth’s own life. We learn, for example, that when she was a child, a running joke in Duckworth’s family was that she and her siblings were not geniuses — yet in 2013, Duckworth won a MacArthur “genius” grant. She pauses to ponder the irony of winning that award for discovering “that what we eventually accomplish may depend more on our passion and perseverance than our talent.” And we learn that as a parent she adheres to the Hard Thing Rule: Her daughters plod away at piano and viola while Mom strives at psychological research and yoga, and Dad at real estate development and running.

“Grit” is a useful guide for parents or teachers looking for confirmation that passion and persistence matter, and for inspiring models of how to cultivate these important qualities. But there are some troubling unintended consequences to Duckworth’s theories. Already, there’s a nationwide push to test students on character attributes such as self-management, conscientiousness — and grit. Duckworth has spoken out against such testing, but the movement has taken root. This year schools in nine California districts will begin giving character-assessment tests. And Duckworth’s book will probably add momentum.

Moreover, in “Grit,” Duckworth dances around the question of poverty. She notes that young children who feel helpless in the face of significant trauma and adversity develop altered brain circuitry that makes it much more difficult to feel the degree of control and hope required for true grit. And she reports that scores on her Grit Scale were a full point lower on average for high school seniors who qualified for federally subsidized meals. Yet she doesn’t offer any solutions for this quandary, apart from quoting one education luminary who says that “what [poor kids] need is a decent childhood” and then describing the importance of extracurricular activities.

But Duckworth’s work, and the move to assess character strengths more broadly, has had some of its deepest impact in schools that work primarily with low-income children. And although her work is clearly well-intended, I worry it may lead our schools to ask and demand the most of those children who are least prepared when it comes to acquiring grit. I worry that the intense individualism embedded in Duckworth’s argument could lead some to judge and critique poor children for their lack of grittiness in the face of immense struggles. And I worry that instead of tackling the gargantuan but essential task of providing poor kids with a decent childhood, we’ll simply — and simplistically — expect them to become paragons of grit.

The Power of Passion and Perseverance

By Angela Duckworth

333 pp. $28