Schools that have embraced digital technology are going cool on cellphones, as evidence mounts that over-using them is damaging children's lives.
Liberal schools such as Albany Senior High School on Auckland's North Shore are still allowing cellphones but are teaching students about how to manage their use of them.
Several more conservative schools, such as Diocesan School for Girls in Auckland and St Joseph's Māori Girls' College in Napier, have banned them in moves which AUT digital education researcher Dr Leon Benade believes "might set a trend".
Benade, who was deputy principal of St Paul's College in Ponsonby until 2007, said most schools banned mobile phones when they first appeared, but embraced them with the arrival of fast broadband and smartphones in the past decade.
"The trend has been to say the phone is an appropriate technology that sits with the other kinds of learning work that is going on," he said.
"In the eyes of those who would argue that the cellphone is a valued teaching device to be used alongside other devices, Dio's approach would seem to be quite heavy-handed.
"On the other hand, it seems to tap into a number of different views. One is that students are over-exposed to screen time, and that social media abuse is particularly bad for young people.
"So I'm guessing that there would be a lot of people cheering from the sidelines and saying that maybe all schools should do the same. It may begin a trend."
Both experts and principals' groups say there is no data on the different approaches that schools are taking, and that the issue is too new for any solid evidence on what is the best approach.
Albany Senior High principal Claire Amos said schools were trying to balance the educational advantages of smartphones and other devices against emerging evidence of emotional harm from over-use.
Top Auckland school bans phones (and the students claim they are happy)
Cellphone ban helps low-decile Māori school top NCEA ranks
She allows students to keep phones with them and to use them without restrictions at intervals, although they are not supposed to use them in class except as "learning tools".
"We encourage students to only have their cellphone out if they need it, but we also recognise that cellphones are often learning tools and they have every reason to use them in the classroom," she said.
"I also recognise that there is some pretty compelling evidence that the amount of screen time that young people are engaged in seems like it is doing potentially some harm."
But she said this was not just a problem for children.
"It can sometimes be ironic if you ask a student about their parents' technology use and they say, 'They never talk to us'," she said.
She said experience with alcohol showed that banning things only drove them underground, so it was better to help young people develop strategies to manage how they used things that could be harmful.
Northcross Intermediate School principal Jonathon Tredray said his students had to put their phones in a box in their classrooms when they arrived at school, and could not use them at intervals, but could take them out of the box when they were needed for learning.
"We are finding they are using them more and more in the class for their learning," he said.
"For example, at the moment they are filming each other doing their speeches and playing it back."
Secondary Principals' Association president Deidre Shea said her school, Onehunga High School, allowed students to use their phones at intervals but they had to turn them off in class.
"Probably that is a fairly typical approach," she said.
"Most schools would have challenges around that at some time. That's probably one of the reasons why some of the schools are swinging back, as well as the lack of social engagement."
Principals' Federation president Whetu Cormick said primary schools were concerned about growing numbers of new-entrant children arriving at school with poor language abilities because both they and their parents have spent too much time on their phones instead of talking to each other.
"For little people, language development happens through conversations with people, not with a screen," he said.
His school, Bathgate Park School in Dunedin, requires children to hand their phones in when they come to school and does not allow them in the playground.
"They should be outside playing with one another," he said.
"We have a policy. If parents require them to bring them [phones] to school, they have to hand it in to the teacher. If they are found, they are confiscated."
Dr Nina Hood, an Auckland University lecturer and founder of the Education Hub , said cellphones could be used to enhance learning, but there was growing evidence of damage caused by "over-connectedness".
"It's as much about supporting young people to understand about proper and effective use of all types of technology," she said.
"It's supporting them to understand when it is appropriate to use a phone, how to use a phone to enhance their learning, and to be aware of the risk."