As with anything online, each of these services comes with caveats.
Snapchat acknowledges on its website that messages aren't guaranteed to disappear: Anyone receiving a text or photo can within 10 seconds capture a "screenshot," taking a photo of their device's screen, and save that image. Video also can be downloaded, although Snapchat says it alerts senders when material is saved.
Instagram is considered tame as long as kids adjust their privacy settings to limit who can see their photos and don't post nudity, which could subject them to child pornography laws. But Levey said many parents don't know their kids are using Instagram until there's trouble — usually when kids post inappropriate photos at parties and these begin to circulate among their social circles.
Parents often hand their kids a mobile device without understanding exactly what it can do, said Dale Harkness, a technology director at Richmond-Burton Community High School in Richmond, Ill. He estimates that even without using social media services, the average high school student probably transmits some 150 texts a day.
"It's not anything that every parent and grandparent hasn't already seen," Harkness said. The problem, he adds, is that actions "get documented, replayed and sent around." He said that students "forget how fast it moves and how far it goes."
Online services also routinely collect personal data, such as a person's birthdate or the location of their phone, and they commonly share the information with third parties for marketing. While a new rule by the Federal Trade Commission this year is aimed at keeping advertisers from tracking kids younger than 13, most social media services require that a user specify he is at least 13, exempting the account from the tougher privacy restrictions.
Levey links her kids' devices to her iTunes account so she's aware of programs they install. She also requires that her kids make their accounts accessible to her and follow certain ground rules: protect your passwords, set privacy controls and never transmit inappropriate pictures or words.
A big hurdle for parents is overcoming the idea they are invading their kids' privacy by monitoring online activity, she said. In fact, she said, it can be the kid's first lesson that hardly anything online is private, anyway.
"If they want privacy," she said, "they should write in a journal and hide it under their mattress."
- NORAD 'tracks' Santa's journey across globe
- Photo gallery: Christmas around the world
- Officer kills armed 18-year-old near Ferguson
- Our six heroes of 2014
- Final goodbye: A roll call of some who died...
- Ex-President George H.W. Bush to stay...
- Severe storms slam the South, killing at least 4
- Blizzard gives Hawaii summits a White Christmas
- Police boss: NYC cops 'quite simply,... 17
- NYPD: Cop ambush killer told passers-by... 15
- Going it alone, Obama rocked the boat... 13
- Officer kills armed 18-year-old near... 10
- Pope in blistering critique of Vatican... 9
- Key developments in the case of slain... 9
- Killings of 2 New York officers trigger... 6
- Senate, CIA agree torture program was... 6