CHICAGO — Keep computers in a common area so you can monitor what your kids are doing. It’s a longstanding directive for online safety – but one that’s quickly becoming moot as more young people have mobile devices, often with Internet access.

A new report from the Pew Internet & American Life Project finds that 78 percent of young people, ages 12 to 17, now have cell phones. Nearly half of those are smartphones, a share that’s increasing steadily – and that’s having a big effect on how, and where, many young people are accessing the Web.

The survey, released Wednesday, finds that one in four young people say they are “cell-mostly” Internet users, a percentage that increases to about half when the phone is a smartphone.

In comparison, just 15 percent of adults said they access the Internet mostly by cell phone.

“It’s just part of life now,” says Donald Conkey, a high school sophomore in Wilmette, Ill., just north of Chicago, who is among the many teens who have smartphones. “Everyone’s about the same now when it comes to their phones – they’re on them a lot.”

He and other teens say that if you add up all the time they spend using apps and searching for info, texting and downloading music and videos, they’re on their phones for at least a couple hours each day – and that time is only increasing, they say.

“The occasional day where my phone isn’t charged or I leave it behind, it feels almost as though I’m naked in public,” says Michael Weller, a senior at New Trier High School, where Conkey also attends. “I really need to have that connection and that attachment to my phone all the time.”

According to the survey, older teen girls, ages 14 to 17, were among the most likely to say their phones were the primary way they access the Web. And while young people in low-income households were still somewhat less likely to use the Internet, those who had phones were just as likely – and in some cases, more likely – to use their cell phones as the main way they access the Web.

It means that, as this young generation of “mobile surfers” grows and comes of age, the way corporations do business and marketers advertise will only continue to evolve, as will the way mobile devices are monitored.

Already, many smartphones have restriction menus that allow parents to block certain phone functions, or mature content. Cell phone providers have services that allow parents to see a log of their children’s texts. And there are a growing number of smartphone applications that at least claim to give parents some level of control on a phone’s Web browser, though many tech experts agree that these applications can be hit-or-miss.

Despite the ability to monitor some phone activity, some tech and communication experts question whether surveillance, alone, is the best response to the trend.

Some parents take a hard line on limits. Others, not so much, says Mary Madden, a senior researcher at Pew who co-authored the report.

“It seems like there are two extremes. The parents who are really locking down and monitoring everything – or the ones who are throwing up their hands and saying, ‘I’m so overwhelmed,”‘ Madden says.

She says past research also has found that many parents hesitate to confiscate phones as punishment because they want their kids to stay in contact with them.

“Adults are still trying to work out the appropriate rules for themselves, let alone their children,” Madden says. “It’s a difficult time to be a parent.”

Mark Tremayne, an assistant professor of communication at the University of Texas at Arlington, says he and his wife put off getting their son a smartphone longer than most- until his 13th birthday, which is quickly approaching. They plan to monitor it, having already discovered a few “surprises” when checking the Web surfing history on his iPod Touch.

On one hand, Tremayne says it’s the sort of stuff he used to look up in books and magazines when he was 13.

“It’s pretty clear that kids will do what kids will do,” he says. But he acknowledges that having a mobile device can make it that much easier to access.

The key, he says, is to talk to his son about it, and that’s what many other tech and communication experts also advise.

At the Conkey household in suburban Chicago, brothers Donald and Harry know their parents track the music they buy and might look at their Web surfing history when borrowing their sons’ laptops. Mom Brooke Conkey acknowledges that she also may glance at the occasional text.

“Oh yeah, she’ll look over our shoulders and she’ll want to know who we’re talking to – and that’s to be expected,” says Harry Conkey, a high school senior. “It’s a parent. It’s natural to want to know who your kids are talking to.”

His parents don’t use filters of any kind because, while there’s been the occasional “mistake” when downloading or surfing on their phones or laptops, Mom and Dad think that’s just part of learning and growing up. That may change, however, with their 6-year-old son Peter.

“I think that things will get trickier as time goes on,” Brooke Conkey says.