National released part of its education policy on Wednesday due to be officially announced tomorrow.
The party wants primary school students' reading, writing and maths skills evaluated by their age rather than a broader curriculum band.
But school principals and the union say it doesn't matter how children are measured if there aren't enough skilled teachers to help them measure up.
When it comes to reading, writing, maths and science Christopher Luxon wants to ensure primary school kids have all the building blocks in place.
But National says to do that the curriculum has to change.
"Rather than having a loose band of a number of years of delivering that curriculum, that we focus it in, year by year so that the knowledge that we need to impart to students is really clear," Luxon said.
Visiting Ōtara's Dawson Primary on Wednesday, the party leader said he is "concerned and alarmed" at the state of education in Aotearoa.
And he wants school children assessed by age group so they don't get lost in wider curriculum bands.
But principals say it doesn't matter how you assess students if the ones who fall short aren't being properly supported.
"Simply saying that they should be here at this date and time, is not going to make that change. What's going to make the difference, is having teachers who know how to respond to the need that's sitting in front of them," Auckland Primary Principals' Association president Kyle Brewerton.
Just last week primary school teachers were part of strike action across the country with calls for better pay and working conditions still unresolved.
"Teachers don't have enough time, they don't have enough resources, and just being told to 'get back to basics', which they've never stopped doing, isn't going to help anyone," Mark Potter, NZEI president
And parents have mixed views.
"It should stay as it is, some kids learn faster, some learn slower, you can't expect a seven-year-old to know what another seven-year-old knows," said one parent Newshub spoke to.
"I think kids all develop at different rates and yeah," said another.
"Keep it as the status quo, and then I think in high school, maybe there's people who will disagree with me because if you don't catch it early, I can see what they're saying," another told Newshub.
Prime Minister Chris Hipkins says there should be consensus when it comes to curriculum.
"Parents, kids, [and] teachers deserve to know that we've got a stable curriculum regardless of who the Government is, and I just don't want it to become a political football."
More details about National's plans to improve education will come when the policy is announced on Thursday.