Primary teachers to strike on Wednesday, is it the high school teachers' turn?

The Post Primary Teachers Association says it's not ruling out strike action if their pay negotiations fail.

It comes on the eve of the first primary teachers' strike in 24 years.

PPTA President Jack Boyle told The AM Show the union isn't thinking about it yet, but it's not being ruled out.

"We've just started preliminary discussions and I think good faith would require us to have quite a bit of talking around what we see as the solutions that are needed for secondary teachers before we start thinking about anything like that," he said.

"What we know is that we need to bring the best people into teaching and we also know that we need to get the conditions of work and the remuneration right so that we can bring out the best in our tamariki mokopuna.

"Talking about whether we're going on strike or not, [when] we've only just sat down to start talking through the correction we need it is a bit premature."

Mr Boyle said the union supports the primary teachers' strike and the fact this is the first strike action in 24 years shows how urgent the situation is for primary teachers.

But it's getting dire in high schools too and something needs to be done to address the growing teachers' shortage.

"We want to establish something to address the fact that forty percent fewer people are coming into secondary education," Mr Boyle said.

"Within the first five years those who do come in forty percent of them are gone and that number's climbing,

"The fact [is] the average secondary school teacher is getting older, we've got one in five secondary school teachers that are older than 60 and almost one in 10 who are older than 65."

Mr Boyle said the union hasn't worked out what they're going to ask for yet and have only just started consulting members, but a 15 percent raise would be a good start.

"Where the money actually goes across the scale is going to be subject to negotiation," he said.

"If you wanted to establish relativity with the median wage such as it was the last time that we managed to get through some pretty severe shortages then you're looking at 15 percent, that's across all the salary steps."