School principals say they're becoming "increasingly concerned" about the pace of change the new Government is "imposing" on schools.
It comes a day after the Government announced major changes to the way literacy is taught in New Zealand.
The Principals Federation warns a raft of changes are happening "without critical consultation with the sector".
"First came cell phone bans, next one hour each of reading, writing and maths, then attendance, and now, we are being directed to implement a structured literacy approach," the Federation said in a statement.
From term 1 next year, all state schools will have to teach reading using a structured literacy approach - which involves phonics, decoding and word understanding.
Education Minister Erica Stanford announced a change in approach on Thursday, which will be supported with $67 million in funding for professional development and resources.
But education unions, including the Principals Federation, worry the government is putting a one-size-fits-all system in place.
"We know that a single option will not be effective in every context or for every student in our culturally diverse country," Federation President Leanne Otene said.
"Mandating a single literacy approach for all schools would be a mistake and would not on its own get the increased achievement rates that we all strive for."
On AM, Stanford said structured literacy works for 90 percent of kids.
"There will be a range of different providers that we will be accrediting.
"The results are just a game-change, especially for our tamariki Māori. They are seeing the biggest gains in reading using structured literacy.
"I'd say to the unions they're on the wrong side of this," she said.
The Principals' Federation says to be successful the changes need to be carefully crafted through collaboration with the sector.
