Principals have expressed relief at the news that teachers will have to be fully vaccinated from next year - though there may be some difficult conversations ahead with staff.

But there's disagreement over whether returning to online learning next week is the right move, with one principal of a low-decile Auckland high school concerned the delay in reopening classes will lead to more lost learning for students.

Prime Minister Jacinda Ardern and Education Minister Chris Hipkins announced this afternoon that all school and early learning staff who come into contact with students must be double-dosed by January 1 next year, and have their first dose by November 15.

Secondary students don't need to be vaccinated but their vaccination status must be registered with the school.

School employees in Auckland and other level 3 regions must test negative before returning to school. Those who are not fully vaccinated leading up to January will have to undergo weekly Covid tests.

Ardern also announced schools in Auckland will not reopen on October 18, the start of Term 4. Further advice would be provided next week.

The New Zealand Principals' Federation's Perry Rush welcomed what he called a "brave decision" from the Government, saying safety was paramount for students and the education workforce.

But he said more nuanced detail had been missing from today's announcement, particularly around the legal and employment status of staff who weren't vaccinated by January 1.

Bruce Jepsen, the president of the New Zealand Māori Principals Association, Te Akatea, said the organisation would support members to meet all the requirements of the law and Covid guidelines.

"Those are the things that play a critical role in having fewer restrictions and lowering alert levels nationwide."

Although Māori vaccination rates are lower than the population average, Jepsen didn't know if that would be mirrored in the education sector.

He would be talking to members in coming days about the implications of the mandate.

"Expert advice - and it's the same for Māori - remains that vaccination is the most effective tool."

Wesley Primary School principal Lou Reddy said he "100 per cent" supported the vaccine mandate for school staff, and it was great news that schools wouldn't open next week.

"For many of our staff there's a sense of apprehension about schools opening before we hit a 90 per cent vaccination rate."

Wesley, a suburb in Mt Roskill, has one of the lowest vaccination rates for the inner city. About 77 per cent of the eligible population have had their first dose, and only 46 per cent are fully vaccinated.

The Shot Bro bus will be in Wesley next week and he hoped the community would get behind the vaccine drive.

"Some of our people are really fearful about getting the vaccine, they're very wary."

Primary school children were particularly vulnerable as they couldn't currently get vaccinated, he said.

"Kids love breaking bubbles. You can't stop a kid from hugging another kid and doing anything a normal human does to show affection and aroha."

Kelston Boys' High School principal Adeline Blair was personally in favour of the mandate but said some staff would have their own reasons for not getting vaccinated.

"Having to work through this is going to be challenging. I am concerned for the impacts on staffing this has the potential to cause and the subsequent impact on learning."

Blair was "deeply concerned" that schools weren't reopening on October 18.

"I hope that NZQA and the Ministry have developed a comprehensive plan on supporting our rangatahi gain their NCEA qualifications as well as support mechanisms for schools in working on bridging the chasm in learning that has developed over the extended lockdown period.

"For our community, online learning does not work well for the majority and every day away from school is another day of learning lost. The wellbeing of our staff and students has been greatly impacted by the inability to interact in person."

Maurie Abraham, principal of Hobsonville Point Secondary School, said he felt a great sense of relief at the decision to mandate vaccination.

"We heard a clear and simple plan - clear test for employees before a return to school, weekly Covid tests until fully vaccinated, and the requirement to be fully vaccinated by January 1.

"These decisions mean that schools will be safe for staff and students. The vast majority of teachers are vaccinated so these decisions should not be a major issue for the profession."

Deidre Shea, principal of Onehunga High School, said the vaccine mandate would be widely supported.

"You can't get 100 per cent [agreement] but I think most parents will be relieved, and most staff and students as well." A few staff might have to have some "tricky conversations", she said. "As human beings we need time sometimes."

She respected the decision to keep schools closed on health grounds even though "we'd hoped against hope they be in a position to be safe to open next week".

Continuing online learning would be harder for those senior students with portfolio work, she said. Some students were also not in a position to continue learning off-site.

She trusted the Government was making the right decision based on health advice "but I sincerely hope it will be safe the week after".

The Early Childhood Council also welcomed the "clear direction" in today's announcement, saying keeping children safe was the top priority.

"The ECC's focus now is supporting our members through overcoming any issues on the way to implementing this mandate."