SAN FRANCISCO — Silicon Valley parents are increasingly obsessed with keeping their children away from screens. Even a little screen time can be so deeply addictive, some parents believe, that it’s best if a child neither touches nor sees any of these glittering rectangles. These particular parents, after all, deeply understand their allure.

But it’s very hard for a working adult in the 21st century to live at home without looking at a phone. And so, as with many aspirations and ideals, it’s easier to hire someone to do this.

Enter the Silicon Valley nanny, who each day returns to the time before screens.

“Usually a day consists of me being allowed to take them to the park, introduce them to card games,” said Jordin Altmann, 24, a nanny in San Jose, of her charges. “Board games are huge.”

“Almost every parent I work for is very strong about the child not having any technical experience at all,” Ms. Altmann said. “In the last two years, it’s become a very big deal.”