WELLINGTON, Feb 9 - Education Minister Chris Hipkins on Thursday brought in a bill that will repeal the legislation that allows for future charter schools.

He said it also allowed the 10 existing schools to continue to operate under their contracts while the ministry discussed options for their future on a case- by-case basis.

But he's made it known what he wants.

"My preferred option is to explore early termination of contracts by mutual agreement," he said.

If early termination isn't agreed, he's retaining the right to issue a notice of termination by the middle of May, effective from the end of the school year.

The primary teachers union, NZEI, says charter schools are a failed experiment and there is no evidence they will add anything to the education system.

"This was just privatisation by way of contract," said NZEI national secretary Paul Goulter.

Mr Seymour, whose party launched charter schools under its support agreement with National, says they have raised student achievement wherever they have been establish and Mr Goulter is "simply wrong".

"Anyone with Google can see that Goulter's claims are untrue," the ACT leader said on Friday.

"The schools have raised student achievement above that of local state schools wherever they have been tried."

National has joined the row with senior MP Judith Collins appealing to Prime Minister Jacinda Ardern.

"What I would really like this government to show leadership on is protecting those poor little kids in charter schools," she said on Newshub's AM Show.

"Jacinda - you're always talking about compassion, fluffing on about it, show some now."

Cabinet minister Phil Twyford, on the same show, said the schools would not necessarily close down.

"They could become a school of special character, they could become a private school, they could become an integrated school," he said.