The full impact of the vaccination mandate for teachers and school staff will not be known until Tuesday, warn principals.
Tomorrow marks the last day for educators to have received at least one dose of the Covid-19 vaccine to keep their classroom jobs.
Principals' Federation president Perry Rush said the vast majority of educators supported the government's science-led approach.
He did not see any point in pushing back the mandate, as firefighters had done.
The government has pushed back the Covid-19 vaccine mandate for the country's 13,000 Fire and Emergency career and volunteer staff until 29 November for "planning purposes".
"The deadline has been known now for a little while and the workforce has been working towards that," Rush said.
"We have to remember of course that many, many teachers, education workers and support staff have complied in good faith."
However, he noted the Education Ministry had not done any data collection, so no-one knew how many teachers will not be able to work from Tuesday.
"My view is that a data capture would have been helpful. I think being as prepared as we can is not an inappropriate thing. However, that has not occurred.
"It will be interesting to see next week if the Ministry of Education moves quickly to do a data capture."
Remote rural schools with few relievers at their disposal were most vulnerable, he said.
Education Minister Chris Hipkins said the mandates were there to protect workers and everyone they come into contact in their jobs.
"Mandating is never easy however we've made decisions around specific workforces, including in the education sector, because we consider that's the best course of action to protect them, their families, communities and those they work with.
"I encourage everyone in New Zealand to get vaccinated against Covid-19 as it is the best thing they can do to ensure their own protection and the protection of their friends and whānau from the virus."