Teachers have launched an attack on middle schools, saying their students could be disadvantaged compared with pupils at traditional secondary schools.
The Post Primary Teachers' Association president, Robin Duff, said it was worrying that the structure of middle schools disrupted students' learning at a critical point.
He said entering high school in the first year of the National Certificate of Educational Achievement assessment could disadvantage them.
A PPTA website also highlighted the concern that the schools did not provide enough of the specialist preparation needed for senior subject study.
Mr Duff said the Ministry of Education appeared to be focusing on building middle schools at a time other countries were closing them because of the duplication of facilities.
However, the ministry said the community was demanding middle schools and research into their effectiveness was under way.
Middle schools take students from Year 7 to 10, spanning the traditional intermediate and early high school years.
The country has six middle schools, with two more planned for Flat Bush in South Auckland.
Albany Junior High School principal Mike Jackson said such questions had been addressed before the school opened in 2005.
The first purpose-built middle school had employed specialist subject teachers and ensured all Year 10s started working towards their NCEA.
The initiative was also backed by research in the US and in Britain.
Mr Jackson said middle schools catered to the specific needs of emerging adolescents. "It's certainly not just done because it is a fad idea."
Last year, Education Minister Steve Maharey asked the ministry to start research on middle schools and develop proposals he could take to the Cabinet.
He was keen to investigate the benefits of the US-style schooling system and said research was needed on "learning and transition" and the most appropriate education for adolescents.
Deputy secretary of education for schooling Anne Jackson said the research was under way.
Communities were being increasingly given more flexibility to decide on schooling structures to meet their needs, she said. A small number favoured middle schools.
"Of the 13 mainstream schools built since 2000, only one is a middle school, Albany Junior High School," she said. "Two more are planned, both in Flat Bush, Manukau."
Stuck in the middle
* Middle schools take students from Year 7 to 10.
* The model is used in the United States.
* Two more are planned in Flat Bush in South Auckland.