All of the content I tutored is available on math websites and in free Khan Academy videos, and every student had round-the-clock Internet access. But even with all that technology, and even at a school with a luxurious 9:1 student-teacher ratio, what their parents wanted for their kids was more adult guidance.

Lakeside parents are not unusual in their valuing of quality time with adults over technology. Other well-educated professionals agree. Silicon Valley executives send their children to Waldorf schools, where electronics are banned until the eighth grade. Steve Jobs once admitted that he didn’t give his children iPads: “We limit how much technology our kids use at home.”

These parents aren’t anti-technology—at work, they tend to be exuberant digital evangelists—but they apparently don’t believe that more machines in and of themselves contribute to education. What is it that they know?

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Over the last decade, I’ve designed, studied, and taught educational technology in different parts of the world. In Bangalore, India, I experimented with multiple mice plugged into a single personal computer to increase student interaction. In rural Uganda, I cringed as students played a typing game with their index fingers, hunt-and-peck style. In Seattle, Washington, I wrestled with the distraction posed by technology in an after-school computer literacy class for pre-teens. Across all of those projects, a single, simple pattern held in every case. I call it technology’s “Law of Amplification”: Technology’s primary effect is to amplify human forces, so in education, technologies amplify whatever pedagogical capacity is already there.

Amplification seems like an obvious idea—all it says is that technology is a tool that augments human power. But, if it’s obvious, it nevertheless has profound consequences that are routinely overlooked. For example, amplification explains why large-scale roll-outs of educational technology rarely result in positive outcomes. In any representative set of schools, some are doing well and others poorly. Introducing computers may result in benefit for some (the ones highlighted in pilot studies), but it distracts the weaker schools from their core mission. On average, the outcome is a wash.

An even bigger problem is that administrators rarely allocate enough resources to adapt curricula or train teachers. Where teachers don’t know how to incorporate digital tools appropriately, there is little capacity for the technology to amplify.

If a private company is failing to make a profit, no one expects that state-of-the-art data centers, better productivity software, and new laptops for all of the employees will turn things around. Yet, that is exactly the logic of so many attempts to fix education with technology.

And what about computers outside of school? What happens when children are left to learn on their own with digital gadgets, as so many tech advocates insist we should do? Here technology amplifies the children’s propensities. To be sure, children have a natural desire to learn and play and grow. But they also have a natural desire to distract themselves with Angry Birds. Digital technology amplifies both of these appetites. The balance between them differs from child to child, but on the whole, distraction seems to win out when there’s no adult guidance. And this is exactly what economists Robert Fairlie and Jonathan Robinson found in a randomized controlled trial of laptops distributed to some California students but not others: Those with laptops saw no improvement “on a host of educational outcomes, including grades, standardized test scores, credits earned, attendance, and disciplinary actions,” though they did use the laptops for social media and video games. That is, if you provide an all-purpose technology that can be used for learning and entertainment, children choose entertainment. Technology by itself doesn’t undo that inclination—it amplifies it.