A directive from the School Trustees Association that principals will be sacked if they don't introduce national standards would prove difficult in Northland, a teachers' union says.
Earlier this year, 80 Northland principals declared their hand by passing a resolution stating that they would not implement the standards as "the effect and impact is so far reaching and unknown".
An email sent to board chairs this week by School Trustees Association president Lorraine Kerr reminds primary and intermediate school boards they are legally bound to implement national standards and can take employment action against principals who block their introduction.
The message warns boards not to sign a petition protesting against national standards and has been described as an "unsavoury turn" by teachers' union NZEI.
It would be "unwise" for any board member to sign a petition against national standards, the email says.
"Employees of the board will need to do what the board requires to implement the national standards, and they will ultimately have to comply with any unlawful instruction or face potential consequences."
Educational Institute president Frances Nelson said the email was a "gagging instruction".
Education Minister Anne Tolley said it was a matter between the NZSTA and its boards of trustees and there was no time to trial the standards.
"We have trialled not having national standards for too long. We cannot continue to let one in five of our children leave school without the basic reading, writing and maths skills they need to succeed."
Mrs Tolley told the Northern Advocate she had received complaints from parents about misinformation used by the unions and principals' federation.
"This is not a political game. These are our children, and they deserve an excellent education, every single one of them."
Ms Nelson said there was a feeling among board of trustees members that the NZSTA was driven by the minister instead of its members.
"They're telling boards of trustees to remove any discussion that's not about implementation, but asking for a trial is hardly an illegal act."
The email was an attempt to close down the discussion at a school and community level, Ms Nelson said.

Boards played an important role in making sure national standards were academically sound, yet many Northland schools didn't have a sense this was the case.
Despite this, their opinions weren't being heard, Ms Nelson said.
And simply firing people would create the problem of how to replace them.
"Northland schools don't find it easy getting staff at the moment anyway and finding people to replace boards will be difficult."

Tai Tokerau Principals Association president Pat Newman said he was surprised that the NZSTA had sent out an "inane circular" instead of finding out what boards or parents thought about national standards.
For that reason the New Zealand Principals' Federation this week prepared a voluntary survey of parents, which some schools would use as an attempt for parents to have a say, Mr Newman said.
A meeting of the Tai Tokerau Principals Association executive in Paihia yesterday reiterated its concerns and misgivings around national standards.
"We will not boycott training as we want to keep the door open to make changes," Mr Newman said.
NZSTA president Lorraine Kerr could not be reached for comment.