Schools are being told that under alert level 3, if a parent or caregiver is still at home children must remain at home.
The update clarifies earlier information from the prime minister about some children returning to schools, once the country enters alert level 3.
Jacinda Ardern announced on Thursday that once the lockdown level changes, early childhood centres and schools would be available up to year 10.
"Attendance is purely voluntary. Our intention is here to create a place for children to go to learn, if their parents need to return to work," she said.
"For children who are able to, we still encourage them to remain home and be part of distance learning."
At the time, the decision was criticised by school principals, who said schools reopening would be a "shambles," with social distancing impossible to enforce.
What does the guidance say?
Additional information provided in guidelines sent to schools by the Ministry of Education now provides more details, restating the need for children to stay at home wherever possible.
Schools and early childhood centres that do reopen will have appropriate measures in place to try to stop any transmission of Covid-19.
This includes limiting pupils to 10 in a group, or 'school bubble', which could then be increased to 20 once all processes are running smoothly.
Under the guidance, early learning centres are advised to increase the room temperature from 16 degrees Celsius to 18C, as well as provide at least 3m per child of indoor space.
Parents are asked to keep sick children at home, and staggered entry and exit times are also recommended.
For schools, specific public health measures are advised, including hand sanitiser available upon entry into classrooms and bathrooms; staggered entry times into classrooms; and contact tracing registers set up.
The advice also directs schools to make children sit in the same seats every day, so that contact tracing is made easier.
In a statement to RNZ, the Secretary for Education, Iona Holsted, said the government has been "very clear that at level 3, parents and caregivers should, where they can, keep their children at home.
"Parents and caregivers best understand their own situation. It is important that schools and early learning centres are physically open for those parents who need them.
"We are working through this with the education sector to find workable solutions."
The president of the Principals Federation, Perry Rush, said the emphasis on students remaining home if possible is sensible.
"That then means that school is open and available to children who need to attend - there could be a variety of young people in that category."
Rush said schools now understand what needs to be done, and will need to undertake planning of their own to find out just which children will be turning up.
"There is a job now for schools to undertake that conversation with their communities to ascertain which children may be in this category, and then of course plan effectively."
Early childhood sector still has questions
The Early Childhood Council said there are still significant questions left unanswered by the Ministry of Education around alert level 3.
The council's chief executive officer, Peter Reynolds, said while it is positive that ideas like staggered pick-up times and social distancing have been abandoned, there are still questions over funding and staffing.
Reynolds said the question of funding for centres is still unresolved especially if they carry on as they have been during the lockdown.
"The approach taken by the Ministry of Education was to effectively provide the subsidies on the basis of enrolment data, rather than attendance, that's worked okay for the past four weeks.
"But what's going to happen when level 3 comes along, and it's sort of like this partial opening process - what happens to the government funding? Are they going to fund on the basis of enrolment as they did before?"
He said he wants to work with both Public Health and the ministry around finding solutions.