In the dark days of 1921, the Massey government prosecuted a teaching student named Hatty Weitzel for sedition for distributing communist literature. because of the support shown for Weitzel by her fellow students, they subsequently passed a law to prevent "disloyal" teachers from corrupting young minds by requiring them to swear an oath of allegiance to the Queen. This law is still in force today, as s162 of the Education Act 1964.
Any enforcement of this requirement is up to individual school boards of trustees as the employers of teachers. Neither the Ministry of Education nor the New Zealand Teachers Council maintain oversight of such affirmations, or enforce or monitor them.So, do schools enforce it? Auckland Grammar doesn't, and I suspect if you asked other schools you'd find they don't bother either. And the reason is pretty clear, as the Ministry of Education notes
In 1921, the main arguments behind introducing the requirement for teachers to swear allegiance to the Crown centred on their role in shaping the minds of children as future citizens [sic] of the British Empire. This is now no longer a key consideration for our society.and yet, the law is still on the books, and could be used at any time to dismiss any teacher a school board didn't like. Which means it has to go. Repeal was apparently part of the oaths Modernisation Bill in 2006, but that was dropped by the National government in 2010. Time for a Member's Bill?