By Kristen Laine

"I put power tools in the hands of second-graders," Gever Tulley often says when he describes the Tinkering School, a one-week camp he started in San Francisco in 2005. The camp teaches kids how to "build anything"—where "anything" can mean a working roller coaster, a car, or a bridge made entirely of plastic shopping bags.

Tulley, who has no children himself, doesn't make it easy for parents who hear "power tools" and immediately think of dismemberment or death. He responds to a question about the wisdom of children using pocketknives by starting a story: "The first time I was left alone with a hatchet...."

Young Gever was not yet a teenager. He'd recently seen a guy at the circus fling a hatchet end-over-end and embed its sharp blade into the butt of a log. He wanted to do the same cool thing. So he lobbed his hatchet at a log. "After 45 minutes, I was so frustrated," he recalls. Not only was he unable to drive the hatchet blade home, he'd also edged closer and closer until he stood right in front of the log, which meant that the hatchet bounced dangerously back at him after each throw. Finally, after more tries and more frustration, Tulley got the blade to stick. But, he says, "I had no idea why that one actually stuck and the others didn't."

This is where Tulley the teacher steps in, and where concerned parents can start to breathe again. Several decades on, well schooled in mechanics and physics, Tulley knows why he had so much trouble during his afternoon of axe-flinging. "There are a huge number of variables in throwing an axe," he points out, "including how far back you stand from the log, where you hold the axe, the point at which you release it..." Mastery comes from getting a feel for angles and speed and motion and making subtle adjustments—the kind of learning, in other words, that happens best through trial and error, from doing and experimenting, not from a book or a screen or in a classroom.

Tulley believes that too few children experience that kind of hands-on learning today and has set about creating a curriculum and a school designed to encourage it. He believes that even young children can follow basic safety guidelines in using knives and other tools. He has distilled some of his lessons into a book, 50 Dangerous Things (you should let your children do), co-written with Julie Spiegler. He points out that in thousands of hours of Tinkering School and other projects with kids as young as 5, he's seen plenty of scrapes, bruises, and cuts—but not a single serious injury.

By giving children the room to explore "dangerous" activities with proper instruction and within reasonable parameters—by letting them learn how to use knives, axes, and spears, maybe even power tools—we give them the chance to learn deeply and become engaged with their world physically, intellectually, and imaginatively. And there's something about the very nature of tools that deepens that engagement and makes it real. Anything sharp or powerful enough to cut, cleave, bore, pierce, crimp, bend, join, or otherwise fashion hard materials is, by definition, dangerous to flesh and bone—and therefore requires respect and full attention. From such engagement comes competence and confidence.

For parents who may still feel reluctant, Tulley offers a few other points to ponder.

Our brains are wired to throw things. Evolutionary scientists suggest that throwing things, walking upright, and developing bigger brains created a virtuous evolutionary circle for humans that lasted millions of years. A child who picks up a spear, finds the balance point, and prepares to launch it embarks on a series of experiments that changes his or her brain. "Each throw is a hypothesis expressed in neuro-muscular control," says Tulley. Throwing a spear, a rock, or a ball stimulates the parts of the brain responsible for visual acuity and three-dimensional comprehension. Refining those throws improves a child's structural problem-solving and predictive ability.

"Combining physical and analytical skills helps develop attention spans," Tulley says. That is, kids learning to throw a spear might get frustrated, but they definitely won't be bored.

Let them learn on their own. Tulley understands that when his younger self threw an axe at a log, part of what he learned was how little he knew. Such lessons prepare the way for deeper engagement. When kids first start throwing a spear, for example, "they're not stating variables," Tulley says. Over time, "Their thinking becomes more subtle than, 'Can I hit the tree?' They start asking, 'What if I change how I hold it, when I release it?' Their understanding becomes clarified."

"If you don't leave them alone for an hour, or more," Tulley cautions, "they won't develop that understanding." Tulley acknowledges that coaching can accelerate the learning process, but says, "It's hard for parents not to get productivity-oriented. That's a trap. We can model for kids, but we also need to let them work things out on their own, at their own pace."

Even young children can understand and follow safety guidelines. In a short talk based on 50 Dangerous Things, Tulley showed a picture of Inuit toddlers cutting blubber with whale knives. "Children are actually pretty good about following conceptual constraints," he says. "You can say, 'Never throw toward a person; always throw toward the tree.' Have them feel how sharp the end of the spear is," or tell them that you'll sharpen it when they've shown that they can be safe with a rounded end. Engaging children's imaginations can work hand in hand with helping them adopt a sense of responsibility.

Giving a kid a pocketknife is like handing over the keys to the universe. "A pocketknife is the original sonic screwdriver," Tulley says—"spatula, scraping blade, screwdriver, pry bar, blade." Kids understand that it has power both as a physical tool and as an imaginative tool. "You can carry it around in your pocket and shape your world," he says. A good portion of that shaping may take place inside a child's head. "Some kids will say, 'I want to make a notch to hold this string,'" Tulley says. "Others will say, 'I'm gonna skin all the bark off this twig,' or 'I'm gonna carve a dragon's head.'"

Tulley suggests that parents establish basic rules with children for using a pocketknife: "Always cut away from your body. Keep the blade sharp. Never force it." And to expect some nicks and cuts in the learning process.

Every child can benefit from learning these skills, but some kids need extra help. Tulley has noticed that some children drift onto what he calls "the track of less and less competence" in the physical world. "Girls are on the receiving end of subtle and not so subtle social pressures to avoid so-called risky behaviors, to avoid being typecast as a tomboy," he says. In Tinkering School he keeps an eye out for "cheerleader psychology," in which girls take a passive role and sit and watch while others do. If a girl continues in such a role, she can become disenfranchised from hands-on activities. Tulley finds that it's useful to engage such girls in small groups, where everyone needs to lend a hand.

Some kids are reluctant to be beginners. When such kids, especially adolescents, see that they are not as proficient as others, Tulley says, it can be a hit to their self-image, which can become a reason not to try something new. Teachers who understand underlying anxiety can help kids overcome it. "That's the beauty of great teaching," he says.