PARIS—Solal Paroux’s friends all have smartphones, and the 12-year-old Parisian has been needling his parents to get him one too. But his parents are resisting.
And now they have the law on their side.
When school starts up in September, a new French law will ban students ranging roughly from ages 3 to 15 from using smartphones anywhere on school grounds, with only narrow exceptions.
The law is one of the most sweeping attempts yet to address growing concerns among parents and educators that a generation of children is growing up addicted to the mobile devices in their pockets.
“Children don’t have the maturity” for smartphones, said Valérie Paroux, Solal’s mother. “Some adults don’t either.”
France’s education minister, Jean-Michel Blanquer, says the ban, which applies to the French equivalent of preschool through ninth grade, is intended to remove distractions during class and to encourage children to read a book or play outside during recreation. He says he hopes the law will serve as a symbolic message to both children and adults beyond school.
“We’re not seeking to reject technological progress—that would be absurd—but rather to master it, to make sure man is the master of the machine,” said Mr. Blanquer, who himself has two smartphones. “It all begins with education.”
In recent months, complaints that big tech firms’ products are too addictive, particularly for children, have started to resonate in Silicon Valley. Facebook Inc. earlier this month said it would start offering tools to show users how long they use its service and alert them to take a break.
Apple Inc. and Alphabet Inc.’s Google each also plans to introduce similar tools into new operating systems for iPhones and Android phones. Apple’s “Screen Time” system will enable parents remotely to monitor the apps their children use and limit their time on devices.
Usage among children and teenagers is growing quickly. In 2017, nearly 79% of people in the U.S. from ages 12 to 17 had a smartphone, up from 62% three years earlier, according to market research firm eMarketer. In France, the figures are higher: 86% of people in that age range had a smartphone in 2017, up from 59% three years earlier, according to the country’s telecom regulator.
Many places in the U.S. and abroad have partially or fully banned mobile phones in schools, but rarely on the scale France is planning. New York City banned student cellphones in public schools for a decade, but ended the unevenly enforced rule in 2015 because of complaints from parents who wanted to be able to reach their children.
There is evidence that a ban on the devices can improve academic performance. A study by researchers at the London School of Economics found standardized test scores for 16-year-olds at 91 U.K. schools measured between 2001 and 2011 rose when they instituted bans on mobile phones. The improvement, equivalent to that from an extra hour of school per week, was greater when the bans were strictly enforced, the study found.
Louis-Philippe Beland, who led the study and is now an assistant professor of economics at Louisiana State University, said France’s ban could help its students. “From our research, it seems very difficult for teachers to police mobile phones,” Mr. Beland said. “So that’s a rationale for being more strict.”
Until now, rules in France covering mobile phones have varied widely. An older law already banned phones in class, but only about half of schools barred them elsewhere in school, according to a parliamentary report.
Under the new law, which the French parliament passed in late July, usage will automatically be barred everywhere in schools, except if teachers wish to use students’ own devices during lessons or if schools establish other exceptions. But the law gives individual schools leeway to determine how exactly to apply the ban.
The education ministry says guidelines it will publish later this month will recommend, but not require, that schools install lockers where students can deposit their phones. Some schools may choose to allow children to keep phones in their bags, however. In any case, the law empowers teachers, administrators and other staff to confiscate phones.
“We want children to rediscover the real, that connection to the concrete, to nature, to do doing things with their hands, to contact with other human beings,” Mr. Blanquer said.
Some parents, teachers and members of France’s political opposition say they are concerned the approach may not be workable—or particularly helpful.
Claire Krepper, national secretary of SE-UNSA, a teachers union, said she thinks the government should have focused its efforts on educating children to use mobile devices “reasonably and respectfully,” rather than banning them.
“People said television would rot our brains and make us couch potatoes,” Ms. Krepper said. “Banning phones won’t solve anything.”
Mr. Blanquer, the education minister, responds that French schools already offer digital education with plans to expand offerings. “There’s an offensive approach and a defensive approach,” Mr. Blanquer said. “We can do both.”
On a recent evening, the Paroux parents expressed support for the law. For some, “it’s like they’re living on social networks,” Ms. Paroux said. “It’s sad,” interjected Stéphane Paroux, her husband.
Solal, for his part, agreed the ban might make it easier for him to be the kid without a phone. But he said he doubts it will be enforceable during recreation in the school courtyard.
“The teachers don’t watch that closely,” he said.
Write to Sam Schechner at sam.schechner@wsj.com