Parents will be required to give explicit permission in writing for their children to receive religious instruction at state schools under a planned law change.
It may be the beginning of the end of primary schools offering religious instruction.
Education Minister Chris Hikpkins told the Herald he believes in secular education and does not believe schools should be offering religious instruction.
"But we need a bit more of a national conversation about that before we get into that," he said.
• Education Minister Chris Hipkins on education changes right across the board
• Premium - Audrey Young: Why Education Minister Hipkins has shot to the top of the class
• Premium - Audrey Young: The curious relationship between Chris Hipkins and Nikki Kaye
• Education Minister Chris Hipkins 'concerned' with maths exam muck up
"I personally hope that as the debate around these things matures, we will reach a point where that provision that allows schools to close for religious instruction is no longer required. That would be a big leap at the moment."
The law change, in the Education and Training Bill which passed its first reading just before Christmas, will require the written consent of parents for their children to attend religious instruction.
It is one of a raft of changes being proposed in the legislation.
Under guidelines released by the Ministry of Education in May 2019, schools are already advised to get the written consent of parents, but the change will make it mandatory.
The Education Act 1964 says that state primary schools should be secular but they are allowed to "close" for the purposes of not being secular and many close for an hour a week to allow volunteers to give religious instruction.
It does not specify which religion but almost all instruction is Christian.
In background papers, the Ministry of Education said it does not collect data on how many schools have religious instruction so it will be difficult to monitor the impact of the change.
But the Churches Education Commission, which has been rebranded as Launchpad, was the largest provider and in 2018 it operated in about a quarter of all state primary schools, or 520.
The ministry expects the opt-in model will have a lower uptake than the current opt-out model, meaning a lower demand for religious instruction.
The cabinet's social well-being committee has also approved Hipkins to direct the Ministry of Education to partner with the Religious Diversity Centre to encourage broader debate about religion in schools.
The main provider of instruction, the Churches Education Commission, in its submission on the ministry's guidelines for religious instruction, said it encouraged schools to be vigilant in obtaining consent of parents, either at the time of a child's enrolment or through signed permission slips at the start of each school year.
"At the start of the school year, remind parents that the classes are available and again seek signed consent for either opting their child into a program or opting them out."
The Secular Education Network is taking a case to the High Court in a bid to get religious instruction in schools declared to be a breach of the Bill of Rights Act.
It expects the case to be heard in October this year in Auckland and has launched a Teach, Not Preach website.
Spokesman Mark Honeychurch said: "Our primary schools are not the place for religious instruction, but we've always had this loophole in the law that enables church members to come in and talk to our children about Christianity; about God, Jesus, heaven and hell."
• Read about more changes planned by Chris Hipkins.