Schools across Ireland have had to deal with more than 200 incidents of cyberbullying over the past year, new research has found.
As concerns over online safety continue to grow, newly-released data also shows that 22% of children are in contact with strangers on the internet.
While seven in 10 teachers report not feeling well enough equipped to teach pupils about keeping safe online.
The children's internet safety charity CyberSafeIreland, which is behind the research, warned that children were taking too many risks online and that teachers and parents were not adequately supported to help protect them.
The organisation found that 179 teachers had been dealing with 219 incidents of cyberbullying over the past 12 months.
It also revealed that 69% of teachers did not feel equipped to teach online safety.
According to the research, 16% of children aged under 13 were spending more than four hours online.
Some 22% of children surveyed were in contact with a stranger, with 14% talking to strangers every week through online gaming or accepting social media requests from people they did not know.
In a third of cases, children have either rarely or never spoken to their parents about online safety.
The research was gathered from over 1,000 children, parents and teachers who attended the charity's training sessions over the past 12 months.
CyperSafeIreland said it was concerned that not enough was being done nationally to address online safety with children.
"As a nation we are failing in our duty to protect our children online," said CyberSafeIreland CEO Alex Cooney.
"If children are online then they need guidance, support and supervision to manage their experiences safely and responsibly, especially when they are young.
"Too often we are seeing children taking risks by sharing personal information in videos and photos, getting involved in incidences of cyberbullying and talking to strangers online."
Ms Cooney said that parents and teachers played a fundamental role in addressing online safety with children.
But she warned: "Our research shows that they are not being adequately supported to take on this role."
Cybercrime investigation specialist and CyberSafeIreland's programme director Cliona Curley warned that the internet presented increasing opportunities for the sexual exploitation and abuse of children.
She said: "Access to technology can be enormously beneficial to children, but we also must recognise that children are developmentally vulnerable, and that they need support and guidance, both to protect them and to empower them to use that access wisely. "
The study shows 32% of children have not spoken to their parents about their online activities.
Ms Curley said parents need to engage with their children's online lives.
"If you want to protect your child online you need to be constantly engaging in their digital lives - you need to be having conversations. They need to know they can come to you if they're worried about anything," she said.