On a late Monday morning in this rural New Hampshire town, Dayna and Joe Martin’s four children are all home. Devin, age 16, is hammering a piece of steel in the blacksmith forge he and his parents built out of a storage shed in the backyard. Tiffany, 14, is twirling on a hoverboard, deftly avoiding the kaleidoscope-painted cabinets in the old farmhouse’s living room. Ivy, 10, and Orion, 7, are sitting next to each other using the family’s two computers, clicking through an intense session of Minecraft.

It looks a lot like school vacation, or a weekend. But it’s not. This, for the Martin kids, is school. Or, to put it more accurately, it’s their version of “unschooling,” an educational theory that suggests children should follow their own interests, without the imposition of school or even any alternative educational curriculum, because this is the best way for them to learn and grow.

“I don’t even know what grades are,” says Orion, who has never spent a day in school, has never followed a lesson plan, and has never taken a test. (Tests, his mother says, can be degrading to children – an invasion of their freedom of thought.)

“We live as if school doesn’t exist,” Ms. Martin explains. “People are really brainwashed into seeing things in school form, with life breaking down into subjects. This life is about freedom and not having limits. It’s about really trusting your kids. And it’s amazing what they do.”

Martin says that, left alone to follow their own interests, her children have learned everything from history and ethics to trade skills and math. But what they learn isn’t her concern, she says. She doesn’t much care if her son knows how to read by age 8. She trusts he will read when he is ready to read. Her role, she says, is not to be her children’s teacher or judge, but a facilitator and perhaps partner in helping them follow their own passions.

Martin is the first to admit that her family’s approach to child rearing might seem, at first glance, “out there.” She is also upfront that it has been lonely at times, disconnected from families whose lives revolve around school, as well as from traditional home-schoolers. But in recent years she has noticed something: She and her family are a lot closer to the mainstream than they used to be.

Over the past decade, the number of children home-schooling has skyrocketed, along with the number of families practicing some form of unschooling. According to the National Center for Education Statistics, the number of children learning at home jumped from just over a million in 2003 to 1.7 million in 2012. But since there is no federal registry of home-schoolers, and many home-schooled children are counted as being in the public school system, many researchers believe the true number is somewhere between 2 million and 3 million, if not higher. To put that in context, the US Department of Education estimates that 2.3 million children were enrolled in charter schools in 2012-13.

Meanwhile, although data are sketchy, some surveys have found that as many as 50 percent of home-schoolers embrace some variety of unschooling – a category that might range from the Martins’ extreme hands-off approach to that of other parents who incorporate many ideas of self-directed learning but still set some limits and goals for their children’s education.

The rise of unschooling parallels a growing dissatisfaction among American parents about the country’s public education system and its focus on standardized testing. It also tracks an increase in alternative educational philosophies, such as the Montessori method or the popular Reggio Emilia theory, both of which are based on the idea of children as “whole,” curious beings whose education should be guided by their own natural interests and inclinations.

But the blossoming of unschooling also reflects something more. While it once was considered a hippie, countercultural practice, experts say that unschooling now taps into changing mainstream values surrounding children and parenting, institutions and individuality, and the best way to seize the American dream.

It also, says Michael Apple, an education professor at the University of Wisconsin-Madison, taps into a growing national sentiment that “safe” and “responsible” private institutions of all kinds are better than public ones that can sometimes be “messy and violent.” Although unschooling has many critics – those who worry about the educational philosophy behind it, those who worry that it reflects a narcissistic culture obsessed with self-fulfillment, those who see it as adding to a disturbing segmentation of American society – it is increasingly accepted as a viable educational option by everyone from soccer moms and urban hipsters to rural Evangelicals and suburbanites.

“I see a shift in the types of people who contact me,” says Martin. “I get calls from doctors, lawyers. I have talked to [professional] rugby players, and low-income people living in trailers. This is not a small subculture anymore. This is a movement.”

• • •

The idea of unschooling is not new. The Massachusetts author and educator John Holt first coined the term in the 1970s as a play on the popular 7-Up “Uncola” advertising campaign. Holt believed that children learned best when given time and resources to follow their own passions outside schools, which he saw as prisonlike institutions that worked to squash inquisitiveness and produce homogeneous industrial cogs.

As an alternative, he suggested parents stand back and let children decide what they wanted to learn. This meant that some kids might never learn algebra, which he believed was just fine; those kids might find their passion in art or cooking. Other children might love math, or marine biology, or architecture, or farming. Although unschoolers follow Holt’s teachings to different degrees of faithfulness, they share the idea of letting children take a central role in how their lives are organized. They typically wake up naturally, have unstructured days, and delve into topics that they have chosen. Parents might act as guides – helping children find information on, say, veterinarian care and then setting up an internship at a local vet clinic – but they are typically followers rather than leaders when it comes to subject matter.

“Unschooling takes learning out of the realm of the school,” says Patrick Farenga of HoltGWS LLC, which works to continue the late educator’s mission. “It’s ‘What do you want to learn today? How do you want to set this up?’ Educators still don’t get this. They have bought into the idea that the only learning that matters is the learning they can grade in school.”

From its beginning, unschooling attracted a small but steady band of followers. “It has had some bohemian chic for 40 years,” says Stanford University sociologist Mitchell Stevens, who wrote the 2001 book “Kingdom of Children: Culture and Controversy in the Homeschooling Movement.” “It was out-there cool when John Holt championed it in the 1970s. It’s always getting rediscovered.”

But increasingly, Professor Stevens and others who have studied unschooling say, the practice is losing its rebel, alternative ethos. Although regulations differ state by state (one reason why accurate statistics on the movement are difficult to pin down), unschooling in some form is legal everywhere in the country. And the families who do it are increasingly mainstream, middle-class, and educated.

In a survey of some 5,500 home-schooling families, filmmakers Dustin Woodard and Jeremy Stuart, whose documentary about unschooling, “Class Dismissed,” came out in 2014, found that the vast majority of unschooling parents (almost 89 percent) were married, and 91 percent had at least some college experience. Almost half live in the suburbs, while the rest are split fairly evenly between urban and rural areas. Almost all say they are satisfied or extremely satisfied with their choice to unschool their children – whether because they have more time as a family, are able to travel more, or see their children learning successfully. While many unschoolers say they are opting out of the national obsession with college admissions and standardized test scores, literature about unschooling regularly mentions how unschoolers are often accepted into top colleges.

All of this, education experts say, means that unschooling is becoming a less risky choice for parents and increasingly represents a viable alternative to a public school system that has received a lot of bad press in recent years.

“My impression is that the drive to unschooling is in part a reaction to concerns that formal schooling has become too standardized,” says Kevin Welner, director of the National Education Policy Center, a Colorado-based research center. “Parents who are looking at sending a child to public school are likely to be more concerned now than a decade ago.”

While some critics have accused unschoolers and other home-schoolers of undermining the public school system by abandoning it rather than working for reform, many parents say they simply can’t wait for better schools. They want to do what’s right for their children now.

This is particularly true, says Cheryl Fields-Smith of the University of Georgia College of Education, among a growing number of minority families. Although home-schooling has the reputation of being a predominantly white enterprise, new statistics suggest that African-American and Latino families make up a rapidly growing number of unschooling families.

In her study of home-schooling families around the Atlanta area, Professor Fields-Smith found that many black families have essentially decided that it is a greater risk to keep their children – particularly boys – in school than to take them out.

For reasons that ranged from the perceived quickness of administrators to label black boys as “troublemakers,” to potential violence at schools, to a desire for a more holistic education at home, black families saw home-schooling as a way to protect their children and give them a better future. And although many black parents started out with more-rigid curriculum plans – “there’s not as much freedom in black families, because they know the odds are stacked against their children as soon as they walk out the door,” she points out – they tended to move toward unschooling as they went along.

At first, Fields-Smith says, this surprised her, given the long African-American history of fighting for quality public education. “But when you dig you see that we’ve always been determined to be self-taught,” she says. “When we were denied resources for school we did it ourselves ... I see this as a new iteration of the long history of [African-Americans] fighting for education.”

Mr. Stuart says that many of the parents he interviewed – black, white, and Latino – simply no longer believe the old equation that public schools will lead to college degrees that will lead to jobs that will lead to a good life. They see a decided lack of stability coming from traditional employment routes, with a particular absence of jobs for the middle class, the socioeconomic group that the vast majority of unschoolers belong to. Unschooling, they believe, may well give their children an advantage in an economy that values fresh, independent thinkers.

This sentiment shows up in Diane Flynn Keith’s unschooling workshops in Silicon Valley. Ms. Keith, who unschooled her own children, says her sessions are filled with tech industry employees and entrepreneurs, all excited about taking a different approach to education.

“People who are involved in the technology industry now, when they’re at work, they’re challenged to think out of the box,” Keith says. “They are challenging old norms. And the moment you begin to challenge one tradition you begin to challenge them all ... then they have children and they begin to think, well, what is this school thing? And why do we keep doing it the same way?”

With more parents taking the unschooling plunge, businesses have grown up to support them. There are international learning trips designed for unschoolers, a popular “not back to school” camp for unschooled teens, and self-directed learning co-ops and various school-like organizations, such as the busy Parts and Crafts Center for Semiconducted Learning in Somerville, Mass. There, 7- to 13-year-olds can either hang out or take classes ranging from computer animation to debate to fantasy geography.

“Look at this,” says 9-year-old Verity Gould, sitting with her laptop one recent morning in the eclectic library area of Parts and Crafts. She was eager to share a few of the cartoon animations she had built with the programming language Scratch. “This is way better than school.”

• • •

But if the perceived educational advantage of unschooling is one draw for parents, there is often also something else. Many of the parents who decide to home-school want a different lifestyle, one that is not only free of what Holt described as the “factory school” and its perceived shortcomings, but one that rejects all of those 9-to-5 obligations that just make life less fun – and, unschoolers would say, less meaningful.

This is what Jamie MacKenzie felt not long after her son, Noah, was born. She remembers watching other parents in her well-off town of Andover, Mass., rush from activity to activity, event to event, with both kids and grown-ups overbooked and overstressed.

“I just knew that wasn’t what I wanted to do,” she says. “As our parenting journey continued, I realized that a lot of our decisions about our values, our health, just the flow of our life, didn’t fit into a normal Monday-through-Friday routine.”

She decided not to return to her well-paying job in education, and instead began a home business with a flexible schedule, selling essential oils. She also decided to keep Noah, now 7, and then her other two children out of school, even though the local school district is considered one of the best in the area. She says her family mostly leans toward unschooling.

All of this has given her family the freedom to travel, to be active, and to socialize with the people they believe share their values, she says.

“The life we have right now has been very intentionally built. This is not an accident,” she says. “And it works for us ... I would never judge anyone for different choices, though. If people want to eat at McDonald’s and go to public school and work traditional jobs, that’s their path. We’ve just been very intentional about the decisions we have made. We are living life by design.”

This desire for “life by design” is no small matter. A number of scholars have pointed out how, over the past half century, self-actualization has risen to one of the country’s most revered values. Americans view it as almost a right to find their “true selves” and “follow their dreams.”

“In general, people are looking for ways to really claim authority over their lives in many ways,” says Stuart. “Not just [in] education, [but also] being unshackled from the 9 to 5 [routine] ... People are starting to question these institutionalized ways of living at all levels.”

They are also starting to question some of the other values of mainstream society, such as working nonstop to accumulate as much stuff as they can. There are simply value choices that you make when you unschool, says Amy Espinosa, who teaches her children at home in rural Georgia and writes “The Little Farm Diary,” a blog about “DIY, lifestyle, homeschooling, parenting, recipes and children.”

“I honestly am more interested in whether my child is a good person – moral, kind, decent, all of those things – as opposed to ‘Can you read by age 6? Do you know your multiplication tables by the second grade?’ ” she says. “Those are not my milestones. I care about, ‘When you are 7, can you talk to an adult? Did you bake cookies for the neighbors at Christmas because your heart told you to?’ ”

Blake Boles, founder of Unschool Adventures, which runs international trips for unschooled teenagers, agrees. “There seems to be overlap with the minimalist-lifestyle people, the voluntary-simplicity people,” he says. “Anyone who is interested in a tiny house is interested in unschooling.”

This is the answer to one of the common criticisms of unschooling overall – that it seems impossible for two working parents to pull off.

“Unschooling is not for everyone,” Stuart says. “However, I will say that more people are capable of doing it than they think they are.”

• • •

But even for those who have decided to trade in jobs and consumerism for simplicity and a back-to-family lifestyle, there can be a catch. It takes an awful lot of work to facilitate all of this self-actualization.

When Devin Martin, for instance, became interested in blacksmithing, his parents were the ones who helped him turn their storage shed into a smithy, helped connect him with a local blacksmith to be a mentor, and worked to help him barter for supplies. They all agree that Devin taught himself how to be a blacksmith. But they also acknowledge that even getting to that point required the family to essentially arrange itself around his and his siblings’ interests.

“There is nothing about this that is lazy parenting,” says Ms. Martin with a laugh.

In her work studying home-schooling parents, Jennifer Lois of Western Washington University in Bellingham, Wash., found that home-schooling mothers, many of whom incorporated some level of unschooling, were both hyperaware and articulate when it came to what was best for their children.

“I saw that moms would talk about all the ways that it was superior parenting,” she says.

They would also talk about how they were exhausted. Active parenting for them was now 24/7, with no letup in all those other household jobs that still fall disproportionately to women. Overall, Professor Lois found that these moms seemed to embrace most tenets of what University of Southern California sociologist Sharon Hays described in the mid-1990s as “intensive mothering” – a set of cultural beliefs that have developed that define “good parenting” as “child-centered, expert-guided, emotionally absorbing, labor-intensive, and financially expensive.” They were, in other words, at the front edge of an idea of parenting and childhood that has become widely accepted over the past two decades.

“One of the legacies of the self-actualization movements of the ’60s was an elaboration of an ideal of childhood – one that was very optimistic and utopian, but also very costly for parenting,” says Stevens. “Because at the end of the day children can’t do everything by themselves. You have to enable them to do things by themselves. That’s the dark secret at the core of progressive pedagogy. It takes a great deal of work to create and maintain conditions under which children can be their distinctive selves.”

Meanwhile, a number of social critics wonder about the darker outcomes of all of this individual fulfillment. Rejecting institutions like the public schools, which – in theory, at least – were supposed to develop a shared sense of culture and democracy, seems to play into a wider problem of a deteriorating sense of community.

“I think there is a broader threat to social cohesion that we’re all living through right now,” says Mr. Welner of the National Education Policy Center. “People see others who are different or who disagree with them as some existential threat. These threats are larger than any threat posed by a small group opting out of formal education. But strong public schools can be a bulwark against the broader threats to social cohesion.”