Parents will decide whether their children need to return to school next week, Prime Minister Jacinda Ardern says.
The Cabinet decision to move to alert level 3 next Monday means that schools will reopen for a teacher-only day on Tuesday April 28 and will be open for students the next day, April 29.
But Ardern reiterated that the Government "encourages" parents to keep their children at home if possible.
"We are not expecting large numbers to be in attendance," she said.
She said about 400,000 people who have not been able to work during the level 4 lockdown will be able to return to work in level 3 in sectors such as construction, manufacturing and forestry.
Many of those people will have children under age 14 who cannot legally be left at home alone, so they need schools and early childhood centres to be open.
Ardern said schools and early childhood centres would not be asked to decide which children can return.
"It would be too much of a burden to ask schools to make decisions about their parent communities. We are not asking them to do that," she said.
"We are asking parents, if you can keep your child at home, you should keep them at home."
Principals' Federation president Perry Rush said most schools would be ready to open by April 29 - the date which the Ministry of Education told them to expect 10 days ago if Cabinet decided to move to level 3 this week.
"Our goal is to be prepared. I think we will be," he said. "My view is that we will cope."
He noted that Ardern said that "the vast majority" of students would still learn from home.
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However he said schools were still waiting for more detail from the Ministry of Education in the next few days on the process to follow on re-enrolling students at school sites.
"We are waiting now on hearing from the ministry around what sort of process we will follow," he said.
He said parents should wait a few days and wait for schools to contact them to find out which children will need to attend school as soon as that process is finalised.
Ardern said "at-risk children and staff" should stay at home and would be supported to do so. Rush said more details on this were also still expected from the ministry.
Auckland Grammar headmaster Tim O'Connor, who earlier criticised the decision to bring back children up to Year 10 simply for "babysitting", said Grammar's leadership team would supervise any students who turn up at school, leaving all subject teachers to carry on teaching all students online.
"All students will go on to online lessons from this Thursday and they will continue until further notice," he said.
"Form 3 and 4 [Years 9 and 10] students who have to can come back on to the campus from the 28th, but it really doesn't have any impact. We won't be encouraging students to do that because there is no advantage to it."
• Level 3 rules for education: covid19.govt.nz.