Teens embracing new services say they don't like the idea of having everyone see all of their random thoughts. They also worry that one wrong move on Facebook could hurt their chances of getting into college or landing a job.

For teens, it has been an essential rite of passage: They turn 13 and join Facebook.

Since she signed up three years ago, friend requests and status updates are as much a part of Meera Kumar’s life as homework and exams at Menlo School, the elite private school in leafy Atherton, Calif., where she’s a 16-year-old sophomore.

But when her kid sister Anika turned 13 last year, she gave Facebook a pass.

“I guess I haven’t been that interested in it,” said Anika, who prefers sharing photos with friends on Instagram via her iPhone or video chatting with them on Google+.

Could Facebook be losing its cool?

With more than 900 million users, Facebook remains the most popular online hangout. But some young people are turning their attention elsewhere. They are checking out new mobile apps, hanging out on Tumblr and Twitter, and sending plain-old text messages from their phones. Their goal is to hook up with smaller circles of friends and share their thoughts and feelings away from the prying eyes of Mom and Dad.

It’s a very grown-up challenge for Facebook, which needs kids to continue to dominate social networking.

Growth in new U.S. users is slowing, and so far, foreign markets, where nearly 80 percent of Facebook users reside, have proved less profitable. The Menlo Park, Calif., company is reeling from its shaky start as a public company. The botched IPO has heightened concerns about its business, particularly its undeveloped mobile strategy, as teen use of smart phones and tablets explodes. Fickle young consumers can make and break social networks, as evidenced by pioneers such as Myspace and Friendster whose appeal faded as tastes changed.

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Researchers who track the technology habits of teens say there is no statistical evidence that Facebook is becoming a teenage wasteland.

“Just because teens are using other services like Twitter and Tumblr more — and they are using these services in huge amounts — doesn’t mean they’re using Facebook less,” said Alice Marwick, a postdoctoral researcher at Microsoft Research, where she studies how teens interact with technology.

In fact, 8 of 10 teens who are online use social networking sites — and more than 93 percent of those users have a Facebook account, according to the Pew Internet & American Life Project. Millions more kids under the legal Facebook age of 13 fib about their age to use the service.

Still, older people are the ones driving much of Facebook’s growth. Users age 50 to 64 made up nearly a quarter of Facebook’s audience in March, according to research firm Nielsen. The only social network with a higher percentage of older users was professional networking service LinkedIn.

Facebook itself is no longer an adolescent. At 8, it’s getting long in the tooth for a social network. And for some teens, the novelty has worn off.