So, a potted history. Or, I suppose, a hypothesis.
The government worried that there weren't enough students in sciences. And so they shifted a pile of tertiary funding into STEM disciplines: Science, Technology, Engineering and Maths. Disciplines that required numerate students but weren't STEM-funding-preferred suffered: economics, finance, and high school maths teaching.
And there's now a big shortage of potential maths teachers. Good experienced maths teachers are retiring and there isn't much of a cohort following behind them. Meanwhile, jobs for science grads can be hard to come by.
There was a decent-looking workaround. TeachFirst would hothouse university grads so they'd be able to jump into the classroom without a teaching degree so long as they had other degrees that would be useful.
The PPTA won a court case knocking them out: the implementation seemed to run against collective agreements. As of December, the government said there'd have to be a review of TeachFirst.
The government might wish to consider whether its STEM funding push has contributed to declining numbers of numerate Kiwi students considering careers in teaching, and consider hastening the review that would let science grads flip quickly into the classrooms where they are needed.