"When it's a week, there's an intensity that takes place. And it would get diluted ... if we had it over a month."
He said he "certainly would never give an answer" that would upset a student.
Mr Key understood the paper would not retract the story as it stood by Mr Marsh's interpretation of his comments.
A spokeswoman for Mr Key earlier said students may have misinterpreted his answer.
Waiuku College principal Tom Vanderlaan did not want to comment today. A staffer said he "just wanted the issue to go away".
"Indigenous language needs more support"
Mr Key should be ready to "nurture" te reo Maori instead of dismissing it as "boring", a language watchdog says.
The Maori Language Commission, or Te Taura Whiri i te Reo Maori, said today New Zealand's indigenous language needed more support - particularly from the Prime Minister.
Commissioner Dr Wayne Ngata said the Prime Minister needed to learn a lesson from the school as well as the student.
"The courage she displayed is a courage we would hope a Prime Minister would display in protecting the indigenous language of a country that requires ongoing support," he said.
"For te reo Maori to survive it must be nurtured at the highest levels. NZ has shown it is ready to nurture te reo Maori and so too should the Prime Minister."
Dr Ngata said it was time Maori language was promoted more intensively and for longer periods of time - exactly what the Waiuku student reportedly put to the Prime Minister at a school assembly last week.
The amount of support for this year's Maori Language Week, which ran from July 27 - August 2, could have "easily" seen it extended to a month, Dr Ngata said.
Staff were still dealing with hundreds of new orders for resources, topping the almost 30,000 resources already sent out in the lead-up to the week, he said.
"Normalising the language into everyday affairs and activities is key and is increasingly becoming a priority for New Zealanders."
