Interviews with Bill Gates, Steve Jobs, Sundar Pichai, and other tech power players reveal that Silicon Valley parents are strict about technology use.

A book suggests the signs may have been clear years ago that smartphone use should be regulated.

There may be a way to integrate tech into the classroom, however, that avoids its harmful effects.

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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: