Online child safety advocate Rachel Downie says parents are unaware of about 80 per cent of what their teen engages in on the internet at home.
Ms Downie, a former teacher, told ABC she had surveyed more than 20,000 students over the last five years, asking "what's something you do on the internet at home that you know you're not allowed to do?"
The results were concerning, with teens viewing violent real-life content, such as fights, muggings and pornography that looks non-consensual.
Photo by Rachel Downie
Ms Downie said 51 per cent of children, mostly boys, had viewed pornography or other illicit material, while one-fifth of respondents admitted to bullying, trolling and stalking for fun.
For some behaviours, the children themselves were screaming out for stronger regulation.
She said parents were often unaware of how far "down the spiral kids are".
"After every presentation, and it's usually with mums, they want to come chat to me afterwards about the fact that their 12, 13, 14-year-old son is addicted to pornography.
Ms Downie said it is a confusing, unchartered time for parents, exacerbated by the demands of school and society for children to be technologically savvy.
"What we're doing is 'ping, you're 12 here's your phone', 'ping you're 13, here's your own computer' and it's happening much earlier.
Ms Downie went on to give advice to parents on what they can do:
Ultimately, Ms Downie said adequate parental supervision and keeping conversations open is the key to tackling the issue.
"If you're not checking you wouldn't know, and it's not good enough anymore to say 'hey my 12-year-old daughter is a great kid, I really trust her'.
"I'm certainly not an advocate for banning everything because that's not the world we live in, but I am a very strong advocate for your need to know what they're doing.
"It's about being a grown-up and being the boss and getting your techno power back and saying, 'look we're going to set some boundaries around this stuff at home'."
Ms Downie said having those conversations with children and teens was crucial to building helping young people cope in the real and emotional online world.
Opening those lines of communication and setting boundaries should be done earlier, than later.