When 10-year-old Caroline* walked into Dr Michael Carr-Gregg's Melbourne office last year, her body thrummed with anxiety.

She and her mother had come to see Dr Carr-Gregg, a child and adolescent psychologist, because the girl had been coerced by a 10-year-old boy at her school into texting him a photograph of her breasts.

"He coerced her in a series of six or seven messages, and finally she did," said Dr Carr-Gregg. "And then he sent it off to 37 of his mates."

The result was catastrophic.

"It was absolutely devastating," said Dr Carr-Gregg.

"She became quite depressed, very withdrawn, she had tummy aches, headaches ... nightmares. She didn't want to go to school. Virtually every development was compromised by what happened to her."

Caroline had to switch schools once her humiliation "became very public". And that was just the start.

Was Dr Carr-Gregg shocked to see such a young girl pressured to take a nude selfie?

After all, high school-age girls have in recent years been the focus of an avalanche of studies and articles about how certain kinds of social media posts, selfies, or followers, can lead to issues like depression, anorexia, bullying, and even murder.

But Dr Carr-Gregg was not surprised by his patient's age, saying that a growing number of primary school-age children were experiencing such problems.

He counsels a girl aged between 10 and 12, who is suffering as a result of social media — she had been bullied, or had a "compromising photo" uploaded — every eight weeks.

"But it's probably a hell of a lot more common than that."

The new challenges of raising pre-teens

So it is, said Susan McLean, a former Victorian police officer and cyber safety expert who gives educational presentations to thousands of children every year.

The minimum age to open an account on many social media networks, including Instagram, Snapchat and Facebook, is 13. ( ABC News: Louise Merrillees )

"I have seen hideous cyber bullying and harassment at that [primary school] age, I've seen exclusion, I've seen kids set up accounts in other kids' names and use that as a tool to bully and harass other people," said Ms McLean.

"I have seen children groomed by predators [on social media sites]" — including some as young as eight and nine.

"I had one parent tell me, late last year, her 12-year-old daughter had been groomed on Yellow to share naked photos with someone who was much older."

Yellow, dubbed "Tinder for kids", is an app that enables Snapchat users to locate people nearby and swipe right or left, in order to become "friends".

All of this puts a new spin on what it means to raise pre-teen girls in 2017.

Whereas just a few years ago, it was 17-year-old girls speaking out about the pressure to mimic Kim Kardashian in selfies, in a "sexual rat race" with teenage boys, now it is not uncommon to hear stories of 11 and 12-year-olds buckling under the same stress.

As Sydney mother Elizabeth* said of her 12-year-old daughter: "Her friends are posting sexually suggestive pics [on Instagram] and now she wants to, too."

More kids using age-restricted social media sites

At the core of the problem, said Dr Carr-Gregg, is the dramatic increase in the number of primary schoolers who own mobile phones.

Whereas four years ago the Australian Communications and Media Authority (ACMA) reported that 35 per cent of them owned a phone, now that figure has hit 50 per cent, said Ms McLean.

And these children are storming social media, frequently on their phones, in even greater numbers.

Dr Carr-Gregg says a growing number of primary school-age kids are experiencing problems with social media. ( Supplied: Dr Michael Carr-Gregg. )

According to the ACMA, only 45 per cent of 8-11 year-olds were using social networking sites four years ago.

But Ms McLean said at least 60 per cent of the 10 and 11-year-old children she saw at schools were on at least one social media site, with the majority using age-restricted platforms.

(The minimum age to open an account on many social media networks, including Instagram, Snapchat and Facebook, is 13.)

While YouTube, Moshi Monsters, Club Penguin and Facebook were the top sites accessed by eight to 11-year-olds in 2013, now that honour goes to Instagram, Snapchat, YouTube and Musical.ly, a social video app that enables users to share home-made music clips.

And the sites in the latter group, said Ms McLean, leave primary schoolers more "prone to danger" due to "limited or no security" (many reveal a child's location) and the fact that they offer live streaming of videos.

Live.ly, the live stream function of Musical.ly, which is extraordinarily popular among primary school-age girls, "is full of predators and those streaming porn and self-harm", said Ms McLean.

Indeed, in December, a father in Wales reported that his daughter was groomed by a stranger on the app to send him nude photos.

And, six months ago, Ms McLean contacted the principal of a Brisbane school after she was informed by a Live.ly viewer that one of the school's 12-year-old female students was streaming videos that featured her cutting herself with a knife.

'Predators aren't interested in you when you're 45'

So why are parents allowing such young children, who until a few years ago were safely preoccupied by Frozen and loom bands, to use these sites?

Because, say experts, many parents do not see the dangers inherent in the sites, as they are forming their opinion of them based on their own experience.

"The predators aren't interested in you when you're 45," Ms McLean said.

"[So parents] think, 'Instagram's really benign, people are only posting food photos, so I can put my eight-year-old on there'."

Children under the age of 13 should not own smartphones, says cyber safety expert Susan McLean. ( ABC News: Dijana Damjanovic )

The average middle-aged mother, in other words, is not going to be contacted by the likes of Fabian Roy Meharry, a well-known Victorian BMX rider and registered sex offender, who in late February faced court over blackmailing children as young as 11 to send him nude photos and videos. (He also sexually abused three of his victims.)

As one Sydney mother I spoke to said of her 11-year-old's Instagram account: "It's just a nice record of her childhood projects."

She feels, as many parents of under-age children using social media accounts I spoke to do, that because her child's followers were part of a social group of family and friends that was known to her daughter, she was not in danger of being preyed upon.

At the same time, many primary schools are failing to teach their students about the dangers of social media, a role that many experts, including Dr Carr-Gregg, believe should be mandatory.

(Australian schools are currently not required to deliver cyber safety education.)

"Sometimes there's the perception [by primary school teachers] that kids aren't on [social media]," said Kellie Britnell, senior education advisor at the Office of the Children's eSafety Commissioner, a federal government agency that provides cyber safety education, both online, and at the request of schools and parents.

"But we've been going in to schools for over eight years. You'd ask the question, 'Put your hands up if you use whatever [social media site]'," and children's hands would shoot up, she said.

"You would see the teacher's faces change. And go, 'We didn't have any idea'."

Aussie kids have the added difficulty of 'dobbing' stigma

In an ideal world, according to experts like Dr Carr-Gregg and Ms McLean, no children under the age of 13 would be on social media, or have a smart phone.

(Should parents want their pre-teen children to have phones for safety reasons, they say, they should instead give them "dumb phones".)

In that respect, there has been some progress.

Last August, Wenona's junior school, a private school on Sydney's north shore that teaches children from kindergarten to Year 6, banned Musical.ly on all devices brought to school.

The same month, more than 100 Year 5 and 6 students from across Victoria debated the topic, "All social media should be banned for children under 12", during a primary school convention at Parliament House in Melbourne.

It is no doubt a development that Dr Carr-Gregg will welcome.

Because while social media problems among primary schoolers has become a global phenomenon, Australian children, he said, have an added difficulty because of the stigma around "dobbing".

"That is unique to our country, and I do think that it exacerbates the problem of many young people I've worked with," Dr Carr-Gregg said.

Caroline, the 10-year-old girl he counselled after she sent a photo of her breasts to a boy in her year, suffered as a result of "dobbing" on him.

"Because of the power of the internet and social media, her reputation as a 'dobber' has actually gone with her [to her new school], and that has soiled her relationships with other people."

Such an outcome is not entirely the child's fault, said Dr Carr-Gregg, but rather a foreseeable consequence of allowing pre-teens, who are frequently uneducated about the dangers and responsibilities inherent to the online world, to communicate over social media.

"The moment you give [that] access to primary school girls, they're going to make mistakes," he said.

"They don't have the maturity to understand the consequences of what they're doing, and they kind of get carried away."

*Names have been changed to protect subjects' privacy.