WELLINGTON (Reuters) - New Zealand school teachers went on strike on Wednesday for the first time in more than 20 years, challenging the Labour government’s plans to balance promised fiscal responsibility against growing demands to increase public sector salaries.

Almost 30,000 primary school teachers did not turn up to work and held protests across the country, leaving parents of roughly 400,000 children aged five to 13 at public schools scrambling to find childcare.

“Teachers and principals voted for a full day strike...to send a strong message to the government that the current collective agreement offers from the Ministry of Education would not fix the crisis in teaching,” said Louise Green, lead negotiator at NZEI, the union that represents teachers, in a statement.

The stand-off with its traditional union support base comes nine months after Labour formed a coalition government, promising to pour money into social services and rein in inequality, which has increased despite years of strong growth.

NZEI said it has asked for a 16 percent pay rise for teachers over two years, whereas the government has offered between 6.1 and 14.7 percent, depending on experience, over three years.

The action comes in the wake of a one-day nationwide nurses’ strike in July and a series of smaller actions by government workers, challenging Prime Minister Jacinda Ardern’s centre-left government.

Arden made a surprise appearance outside parliament on Wednesday with a group of ministers to welcome the more than 1,000 protesting teachers.

“There is no you and us, there is only us,” she said on Television New Zealand footage, to applause from the crowd.

“The only point we would make is unfortunately sometimes radical change takes time. So I’m here today to ask you to work with us as we try and move forward.”

Wage growth has remained sluggish in the island nation for years, despite soaring housing costs, which labor groups and economists say has left workers struggling despite robust growth.

Labour has put raising workers’ wages at the heart of its policies, lifting the minimum hourly wage by 5 percent to NZ$16.50 in April, with further plans to hike it to NZ$20 by 2021, as well as rolling back restrictions on union bargaining power.

Business confidence in New Zealand is at a 10-year low and economists and the central bank are worried higher wages could hamper growth if firms’ hold off on further investment.