Seymour said partnership schools - which are privately-run but publicly-funded - were well placed to teach science, technology, engineering and maths.
"Partnership schools could, for example, hire scientists and other Stem experts, and would have flexibility in setting remuneration for Stem teachers."
Labour's education spokesman Chris Hipkins said the change was a major move to expand charter schools that had "huge ramifications" for parents with children at state schools.
He said the announcement on the last day of Parliament was cynically timed to avoid scrutiny.
"The idea that these schools were introduced to help priority learners was always a weak facade for the policy's true intention that has now been exposed.
"Charter schools are nothing more than the wholesale privatisation of our world class education system. To say they're about improving our kids' education or offering more choice for parents ignores the vast evidence about the schools both domestically and internationally."
Stem-focused partnership schools can apply to an application round early next year, with schools to open in 2019. There are currently eight partnership schools.