"The pace of change is ludicrous," Waverley Park School principal Kerry Hawkins, of Invercargill, said.
He believed the government was well out of its depth trying to get teachers and pupils to adjust to the new curriculums for maths and English so quickly.
They are set to be introduced in term 1 next year.
"I don’t think they fully understand what they’re doing."
Teaching staff had been sent an "impossible list" of webinars to attend that barely left any time for teaching, he said.
On Monday there was one for maths then on Tuesday and yesterday there were webinars for English and attendance respectively.
On December 2, 3 and 4 webinars were scheduled for the arts, health and physical education and social sciences.
"That is insane," Mr Hawkins said.
"I suppose we waste potentially eight productive hours a night sleeping. We could do it then."
The new curriculum was set up to teach children by year level but many schools had multiple year levels in one class so it reduced a lot of the flexibility for teachers to work in those environments.
"If you try to do it the way it is written, it’s just not doable."
He said that, realistically, teachers would not be ready to teach the new curriculum next year.
Nonetheless, he was not surprised the government had not taken that into consideration given the limited amount of consultation with teachers regarding the changes.
"When we have been ‘consulted’ we haven’t been listened to anyway," he said.
Consultation felt like shouting into an "echo chamber" at this stage: "They’re hearing what they want to hear."
His advice to teachers was to just breathe.
The average age of teachers was creeping up and there was not much replacement stock in the pipeline.
A lot of teachers were looking to leave because they had simply had enough.
Mr Hawkins was worried a lot of neurodiverse pupils would be left behind with the new curriculum.
Teachers would struggle under the workload to make students feel safe and manage the classroom.
Not all children learnt the same way and it would be difficult to get them to self-regulate under the new curriculum.
He said Waverley Park used a successful research-based, New Zealand-made maths programme to teach called Developing Mathematical Inquirer Communities.
An NZEI Te Riu Roa spokeswoman said the government’s new approach to learning removed the inclusivity and flexibility teachers need to ensure every learner thrived.
It placed unrealistic expectations on children with ADHD, autism and learning differences.
Education Minister Erica Stanford said while change was difficult, support was available for principals who thought there was a lot coming at them.
"We’re there to make sure we’ve got resources, really good implementation, that we’re feeding back results early. We’re putting intervention teachers in to help those students who are falling behind. We’re doing everything we can," she said.
