An Auckland academic wants teachers to be given one day off a week to talk with their colleagues about what is going wrong in the classroom.
Giving teachers time away from the classroom is more important than smaller classroom sizes, the University of Auckland professor believes.
John Hattie's book The Visible Learning Lab is based on his international study of up to 200 million children.
It is a summary of 50,000 studies carried out over 15 years which looks at what makes a difference to student achievement.
Professor Hattie suggests teachers need to seek more feedback on which students they are not reaching and wants teachers to work towards having classrooms where students can freely admit when they do not understand.
The Auckland University academic believes too much of what teachers discuss with one another is about test scores and curriculum, and not about their own teaching.
Professor Hattie says the best schools are the ones where teachers can freely admit they need to change their teaching style.
He says rather than reduce class sizes, teachers need to take more time to work with their colleagues, look at particular students, and get away from the present system where one teacher has one set of students all year.
Professor Hattie says many New Zealand teachers are already doing this, but it needs to be given more consideration.
He says a similar policy has been successful in Denmark.