Mark Zuckerberg knows a lot of things, but parenting, it seems, may not be one of them. The CEO prohibits underage users from breaching Facebook’s walls, but 21% of kids six to 12 are still finding their way onto the world’s largest social network, and 79% of their parents are not only condoning it, they are also openly ‘friending’ their kids.

The figures come from the third consecutive LMX Family study, a US-based syndicated research program that provides trended data on kids’ media habits. The February 2011 study commissioned by Ipsos, which surveyed more than 2,000 kids ages six to 12 and 715 parents of preschoolers, points to a growing level of co-entertainment among parents and kids alongside a softening of parental perceptions of age-appropriate media.

Given that media activities currently make up more than a quarter of a six-to-12 year-old’s waking day, technology is significantly altering the way parents are parenting, says Donna Sabino, SVP of Kids and Family Insights at Ipsos OTX Media CT.

“A child’s first cell phone, first game system and his or her exposure to technology are all happening earlier. Parents used to be focused on standard ratings but we are seeing a lot more parents deciding what is and isn’t appropriate for their kids,” says Sabino. For example, the study finds that 51% of parents of boys ages nine to 12 are allowing their sons to play mature-rated video games as long they are supervised. And 70% of parents surveyed say they endorse their child watching a PG13-rated movie. Video websites in general are attracting younger audiences, as 35% of kids ages six to 12 are frequenting YouTube, a 9% increase from last year.

Looking at the numbers, Sabino says it is crucial for marketers to determine how parents are measuring what is and isn’t age appropriate.  “Your brand may not be a part of the kid market, but Mom may still be inviting you into her house earlier than you had imagined.”

Also important for marketers is the fact that while watching live TV is still the dominant media activity for this age group, kids are increasingly going online, video gaming and using cell phones while watching. Roughly 36% of kids go online while watching live TV and 30% are visiting social networks. Television in general presents the biggest co-entertainment opportunity for families, as 94% of parents are watching television with their child.

“It comes down to functionality rather than labeling,” Sabino says. “Facebook, for instance, meshes with kids developmentally speaking, and parents want to find entertainment they know their kids will like.”