Steve Jobs did not let his children play with the iPad he helped create. Justin Sullivan/Getty

Psychologists are learning how dangerous smartphones can be for teenage brains.

The World Health Organization recently advised parents to limit screentime to just one hour a day for children under five. Though one large study found little correlation between screen-time and mental health impacts, other research has found that an eighth-grader’s risk for depression jumps 27% when he or she frequently uses social media.

But the writing about smartphone risk might have been on the wall for roughly a decade, according to educators Joe Clement and Matt Miles, co-authors of the book “Screen Schooled: Two Veteran Teachers Expose How Technology Overuse is Making Our Kids Dumber.”

It should be telling, Clement and Miles argue, that the two biggest tech figures in recent history — Bill Gates and Steve Jobs — seldom let their kids play with the very products they helped create.

“What is it these wealthy tech executives know about their own products that their consumers don’t?” the authors wrote.

Here’s how Silicon Valley elites limit screentime for their own kids, despite helping sell tech to children across the world:

Bill Gates, one of the most influential tech leaders in the world, limited how much technology his children could use at home.

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In 2007, Gates, the former CEO of Microsoft, implemented a cap on screen time when his daughter started developing an unhealthy attachment to a video game. He also didn’t let his kids get cell phones until they turned 14.

Other techies, like Snapchat CEO Evan Spiegel, limit their kids’ screen time.

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Spiegel and his wife Miranda Kerr impose an hour and a half of screen time per week on their kids, he told the Financial Times. Young people use Snapchat more often than any other social media platform, according to a 2018 Pew Research Center survey.

Plus, current Apple CEO Tim Cook and Microsoft CEO Satya Nadella have spoken out against tech overuse among children.

Despite the fact he created the iPad, Steve Jobs wouldn’t let his kids use it.

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Jobs, who was the CEO of Apple until his death in 2012, revealed in a 2011 New York Times interview that he prohibited his kids from using the newly-released iPad. “We limit how much technology our kids use at home,” Jobs told reporter Nick Bilton.

In an recent interview on Cheddar, iPod co-creator Tony Fadell speculated that if Steve Jobs were alive today, he’d want to address growing societal concerns about tech addiction. “He’d say, ‘Hey we need to do something about it,'” Fadell said.

The CEO of Google’s parent company, Sundar Pichai, limits the time his kids spend watching TV.

Google CEO Sundar Pichai speaks during the Google I/O keynote session at Shoreline Amphitheatre in Mountain View, California on May 7, 2019. JOSH EDELSON/AFP via Getty Images
Pichai told the New York Times in a 2018 interview that his then-11-year-old son did not have a cell phone, and that he limits the time his children spend watching television.

Even elite Silicon Valley schools are noticeably low-tech.

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That’s at the average school at least, according to the coauthors. A number of specialty Silicon Valley schools, such as the Waldorf School in Mountain View, are noticeably low-tech. They use chalkboards and No. 2 pencils. Instead of learning how to code, kids are taught the soft skills of cooperation and respect.

At Brightworks School in San Francisco, kids learn creativity by building things and attending classes in treehouses.

Some low-income schools, meanwhile, have increased their tech usage to help solve for teacher shortage problems. Parents said a Mark Zuckerberg-funded web-based teaching platform caused physical and mental ailments, The New York Times reported.

Despite barring his own kids from using too much tech, some experts say Gates touts the use of electronic devices in schools.

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If there is any concession Gates has made on technology, it’s in the benefits it offers students in certain educational settings. In the years since Gates implemented his household policy, the billionaire philanthropist has taken a keen interest in personalized education, an approach that uses electronic devices to help tailor lesson plans for each student.

In a recent blog post, Gates celebrated Summit Sierra, a Seattle-based school that takes students’ personal goals — like getting into a specific college — and devises a path to get there. Teachers in personalized learning settings take on more of a coaching role, helping to nudge students back on track when they get stuck or distracted.

Technology in these cases is being used as specifically as possible — and in ways Gates recognizes as useful for a student’s development, not as entertainment.

“Personalized learning won’t be a cure-all,” he wrote. But Gates said he’s “hopeful that this approach could help many more young people make the most of their talents.”

Authors Clement and Miles make the case that while Silicon Valley elites have made a profit off of selling tech to kids, they recognize how addictive and harmful these products can be.

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In “Screen Schooled,” Clement and Miles make the case that wealthy Silicon Valley parents seem to grasp the addictive powers of smartphones, tablets, and computers more than the general public does — despite the fact that these parents often make a living by creating and investing in that technology.

“It’s interesting to think that in a modern public school, where kids are being required to use electronic devices like iPads,” the authors wrote, “Steve Jobs’s kids would be some of the only kids opted out.”

Jobs’ children have finished school, so it’s impossible to know how the late Apple cofounder would have responded to education technology, or “edtech.” But Clement and Miles suggest that if Jobs’ kids had attended the average US school today, they’d have used tech in the classroom far more than they did at home while growing up.

Chris Weller contributed to a previous version of this article.