Some teachers are not meeting a requirement to learn and use te reo and tikanga Māori.
Teachers must declare that they are developing and practising te reo and tikanga to renew their annual practising certificate.
But a Ministry of Education paper to Associate Education Minister Kelvin Davis this year said the Teaching Council was not applying the requirement to all teachers.
The Teaching Council told RNZ of 28,689 applications to date there had been 300 "no" responses to the question "Has the teacher continued to develop and practise te reo me ngā tikanga Māori while practising as a teacher?"
It said reasons given included that the teacher was a relief teacher and therefore unable to provide full evidence of fulfilling the requirement, had recently returned from overseas, or needed more time.
The council's chief executive, Lesley Hoskin said the requirement had been part of teachers' professional standards for years, but this year the council made it an explicit part of the recertification process.
She said teachers must formally declare they have met the standard and their principal or the manager of their early learning service must attest that is correct.
However, she said some principals or managers had not "ticked the box".
"If they don't it tick it they have to add a comment, and the comments are generally around this person's beginning, we haven't done a lot in the school, or actually they're fluent and what progress would I expect them to have," she said.
Hoskin said in those instances the council was trying to identify what support teachers needed to progress their knowledge.
She said the goal was to have a teaching workforce that was able to meet the needs of every learner, including Māori children who had been under-served by the education system for years.
"My hope would be that every one of our 138,000 registered teachers were comfortable and confident to speak te reo Māori and understand the tikanga in each local setting," she said.
Hoskin said a handful of teachers might not advance their knowledge of te reo and tikanga, and the council would deal with that group eventually.
"At that point we'll have to look at how many and what's needed and what opportunities have they had. But from what we can see, people are not resisting, what they're saying is I don't know how or or I need support, or I don't have time," she said.
Hoskin said the council might give teachers the benefit of the doubt initially, but it would not tolerate teachers who repeatedly failed to meet the requirement.
"We've just moved to a one-year renewal period for a certificate so if they're not progressing the first time, you're going okay, we've made that known that that's a requirement, if it happens a second or third time the conversation is quite a different one," she said.
"We'd have a conversation to say to the principal what's happening, what do you need to be doing here because they're not meeting the expectations."
Hoskin said knowing te reo and tikanga was no different from other requirements expected of teachers.
"An education system that works in this country within its culture and context is what we're trying to create because then we'll have all of our children being successful and therefore a great country at the end of it because we'll all have those skills," she said.
The principal of Te Whata Tau o Putauaki and a member of the council's board and of the NZEI executive, Ripeka Lessels, said principals must be able to put their hands on the hearts and assert that their teachers were meeting the requirement.
"There is no excuse now for not doing it, but they now need to ensure that their staff are progressing along a continuum that grows their capacity to speak te reo Māori but also to work with Māori children and their whānau ," she said.
She said schools also had to teach the stories of the tangata whenua in their region and the requirements applied to all schools even if they had few Māori children.
Lessels said the requirement was long overdue and it should have a huge impact.
"The impact of this, I believe, will see a lot more particularly tamariki Māori achieving at better rates than we're seeing today because the teachers that are front of them genuinely understand what manaakitanga means, what whanaungatanga means, all those things that build self-esteem in our children," she said.
"There'll be lots and lots of children who will not be falling through the cracks or not be this long tail of underachievement."
Principals' Federation president Perry Rush said he expected all teachers would eventually have to meet minimum levels of competence in te reo Māori.
"This is an official language, it should have equal status to English, ultimately that's where we want to see it in our schooling and it's going to take some effort to get there, but we have to be prepared to work hard, we have to prepared to make sure that there's great resourcing in place and that there are minimum expectations around minimum competency in te reo Māori in our teaching profession," he said.
Last year, the Government said all schools, early childhood centres and tertiary institutions should use te reo Māori every day.