In a bid to protect students from pornography, predators and other online dangers, some schools are turning to technology that notifies teachers, parents and welfare staff when students access concerning material on their mobile phones.

But students and privacy experts have raised concerns about the initiative, which they say erodes trust and puts children under unnecessary surveillance.

The surveillance tool, which has been developed by Australian company Family Zone and is being rolled out at 40 schools, can also block students' access to inappropriate internet sites and "distracting" phone apps.

It solves the issue of students bypassing filters on their school's internet network by using their personal phones.

Schools have a duty of care to ensure students don't put themselves at risk, Family Zone vice-president of education Robert Smyth said.

"If something goes wrong with that mobile device and the school has endorsed it then you can imagine there are all sorts of legal implications," he said.

Parents have to give permission for schools to use the technology, and can extend the surveillance into their homes.

It relies on students downloading a tamper-proof phone app, and a portal lets parents see what sites, messages and apps children are accessing. Schools and parents can deactivate the phone's cameras and a sleep timer bars students from accessing the internet at bedtime.

"If the school is having a school swimming gala they don't necessarily want kids taking photos and posting those photos," Mr Smyth said.

Marist College Bendigo decided to roll out the technology after fielding calls from parents who wanted more control over their children's phones.

The school's technology leader Tony Hoye said parents and teachers would soon meet to decide which search terms would trigger an alert to wellbeing staff at the school and families. These might include suicide, eating disorders or the adult dating app Tinder.

"It is always a worry to supply devices to your kids. You don't know what they are up to and when they are at risk," he said. "This give parents a bit of control back and visibility. The monitoring is to start a conversation between the parent and the child rather than a punishment type of scenario."

While Marist College parents will have the option of seeing what their children are doing on their mobile phones, the school said it would not be utilising this function.

But Victorian Student Representative Council executive student Spencer Davis – a Year 11 student at Footscray City College – said the technology undermined children's agency because it did not require their consent.

"It has an Orwellian feel to it. It's invasive and unfair," he said.

He said that he had no issue with schools monitoring what students did on their network, but delving into their private devices was concerning.

Australian Privacy Foundation chair David Vaile described the technology as a "privacy intrusion".

"Kids want to live a separate life to their parents and there is a risk this could isolate young people ... rather than opening up you feel like the object of surveillance."

He said that there was great scope for businesses to "whip up fear" about the online world.

Invasive school surveillance practices are on the rise, according to University of Adelaide Associate Professor Andrew Hope. These include swipe cards and biometrics which detect when students arrive at school, CCTV and online monitoring.

"In the last five years it has leapt out of the school environment and gone into student's homes, using hardware on their laptops and phones," he said.

While the safety of children is important, Associate Professor Hope said children had a right to privacy and surveillance devices could make them less engaged, stigmatise them and erode trust.

Clarification: This story was edited to say that while Marist College parents will have the option of seeing what their children are doing on their mobile phones, the school will not be using these powers.