Stuff political editor Tracy Watkins talks to Prime Minister Jacinda Ardern, who suggests teachers should have stayed around the negotiating table longer before deciding to strike.

Teachers need to stop sulking and realise every job is hard, says one deputy principal, as almost 30,000 of his colleagues strike.

The acting deputy head teacher at a school in the Nelson region said: "Look, teaching isn't a walk in the park. But it's a pretty sweet gig."

The man, who doesn't want to be named for fear of jeopardising future job prospects, will not be on Wednesday's picket line.

NEON BRAND/UNSPLASH One deputy principal says he's annoyed with his colleagues for striking. (File photo)

"I'm so annoyed with my fellow teachers," he said.

He said he believed there was no good reason for the strike.

"So we're undervalued - in our eyes - and we've 'only' had inflation matching increases for the past decade. Join the queue with the nurses.

"So we're doing a really tough job with increasingly demanding 'customers'. Join the queue with the retail sector."

Teachers walking off the job when they don't get their way doesn't set a good example to the kids they teach, he said. "I don't believe in sulking."

"I don't think a strike really fits with [...] being resilient, having a positive attitude and persisting, all the things we're trying to instil in our kids."

He said he "disagrees fundamentally" with what the unions are after, saying the demands for an increase in pay and smaller class sizes benefited teachers, not students.

He'd rather see that money poured in to putting more adults in the classroom, giving each class a dedicated teacher aide, in a similar model to the Finnish system.

DOUG FIELD/STUFF One deputy principal won't be seen on the picket line on August 15.

He became a teacher a decade ago after a seven-year stint in private equity in London and Auckland.

While he's currently acting deputy head, the size of his school means he's full time in class teaching.

Teachers who think they'd have an easier ride in the corporate world are wearing rose-tinted glasses, he said.

"You want your 2 to 3 per cent pay rise every year in a private company - you better bloody earn it."

Before studying, he interned at two schools on Auckland's North Shore. The "wonderful" experience convinced him it was time for a career change - which also meant turning his back on a six-figure salary and an annual 20 per cent bonus.

But while the money may not be quite as good in teaching, he said his workday was now considerably shorter than it was.

"I'm away from work by 4pm almost every day, answer a few emails in the evening and mark for an hour on Sunday during term time. That's it.

"I was doing far more in London when my day would begin with a 6am commute [...] or in Auckland where leaving the office before 5pm was frowned upon even on Friday."

In the run-up to the strike, teachers have been vocal about their workloads - it's more than a 9 to 3 job, they say.

So what does he say to the teachers complaining of being overworked?

"Work smarter [...] Become more efficient."

There's "a bit of 'woe is me'" in their complaints, he said, and teachers needed to accept working in the evenings was part of most jobs.

As for the teachers who said they worked through the holidays - he was sceptical.

"Anyone who says they do is either pulling your leg, mistakenly remembering, playing the martyr, or terrible at managing their time."

He said while spending holidays working may be necessary in the first few years, after that teachers should have resources and lessons under their belt.

"It's that initial two to three years that's hard - after that you're on easy street.

"Two solid eight-hour days in the holidays and I can prepare everything I'll need for the next 10 weeks."

If you factor in teachers' 12 weeks of holiday into their salaries, the money is pretty good too, he said.

"We got into this with our eyes wide open, it's very well publicised what the pay scale is."

Pay is one of the main things at stake in Wednesday's strike. Teachers' union the New Zealand Educational Institute (NZEI) is seeking a 16 per cent pay rise over two years for teachers.

The union said a pay jolt was needed to attract and retain teachers, but he didn't think more money would help the sector's retention problem.

The things likely to drive teachers from the profession were stress, exhaustion, and the increasingly demanding nature of children in today's classrooms due to things such as mental health problems, he said.

These problems would be better addressed by getting more teacher aides into classrooms to share the load. He said utilising final-year teacher college students would be the ideal solution; the students would get an idea of the realities of teaching - plus a wage - and teachers and children would also benefit.

However, he didn't see that happening; the union is the voice of teachers, and in his opinion it always asks for the "wrong things".

On strike day, he'll be at school with other non-union members of staff to supervise any children who come in.

Teaching is a "brilliant, rewarding" job, he said.

"In fact, the only time I don't enjoy my job is [...] when little kids throw a tantrum and down tools, refusing to do what they need to do. But I guess to be fair the kids didn't choose to be in school.

"They can't leave and get a better daily grind elsewhere. But perhaps some teachers should."

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