An Auckland school has told parents they must put "spyware" on their children's phones for the children to get access to the school's Wi-Fi network.
The Council for Civil Liberties says the move by Birkenhead College is "a step too far".
But college principal Craig Waller says the phone app, Family Zone, "is set up so that we help our students focus on their education and they are not exposed to unsafe or inappropriate material".
The app lets parents manage their children's devices in and out of the home, including setting turnoff times, limiting downloads and purchases, blocking pornography and restricting access to games, social media and adult-rated YouTube content.
The system sorts websites into risk categories, sends parents an alert when a child tries to access a high-risk site, and emails parents weekly reports on what sites their children have looked at.
A Birkenhead College email to parents told them to expect an email from Family Zone, and advised: "Please read it and keep your parent password safe. [Child's name] will thank you for that, as he will soon not be able to connect his phone to our school Wi-Fi without you authorising the company's app on his phone."
It added: "Please consider purchasing a Family Pack for $40." A pack allows parents to monitor six phones or other devices.
A father who was asked to sign up to monitor his 15-year-old son said he was surprised that it was not optional.
"I may sound naive, but I think to actually ask him what he's reading and doing, and to set some boundaries and guidelines for him and let him show that he is responsible, is the style of parenting that I'm okay about," the father said.
"I wonder if this app, rather than the schools, are going beyond that."
Council for Civil Liberties spokesman Thomas Beagle said controlling internet access outside the school "should surely be between the child and the parent".
"You can see why a school might want to build some obligation into its access policy, but the next level up of what is basically spyware, and reporting what you have done to someone else, seems a step too far," he said.
Family Zone is a company listed on the Australian Stock Exchange. Its NZ general manager Colin Hogg said the school app was originally developed in Christchurch in 2014 as "Linewize", but was sold to Family Zone in 2017 to extend controls beyond the schools' own wireless networks.
"When I was meeting principals back then, one of the problems that was always highlighted was that it keeps the kids safe in the school Wi-Fi, however when they jump off the school Wi-Fi they can go wherever they want," he said.
He said almost 300 schools in New Zealand, 150 in Australia and 200 in the United States have bought the app so far.
Waller said Birkenhead College students could still access the school Wi-Fi on school computers if their parents did not sign up to the app, but the app gave them Wi-Fi access on their personal phones and laptops as well.
"They can access our Wi-Fi once they get the app on any device they bring to school, and can also access the Wi-Fi using our school devices," he said.
Netsafe education and engagement director Sean Lyons said all schools were wrestling with the issue of how to provide internet access for learning but not for other uses such as porn. Some set time limits such as allowing personal Wi-Fi access at lunchtimes, and some banned personal devices completely.
"If what they are saying is that without this tool we will not allow the use of personal devices on to our network, that is perfectly acceptable," he said.
"There is no compunction for any school to allow personal devices that are not used in a learning context to connect to the school network."