Twenty-four schools in Hawke's Bay have more students than the Ministry of Education provides to educate them.
Ministry figures provided to Hawke's Bay Today under the Official Information Act reveal 24 schools in the region have more students than teaching space.
Mahora School principal Rohan Pearse said the roll had steadily grown to 401 students, 29 more than the school's enrolment zone capacity.
He said the growth had forced the decile 3 primary school to teach two classes in the library but it wasn't a problem.
"It's not ideal but it's the best we can do. It's a fabulous learning space.
"We're pretty disappointed that we've had to move our library to the hall but obviously, going forward, we're looking at other ways we can manage the growth we're experiencing."
Mr Pearse said the ministry had been happy to discuss new building plans to account for the roll growth and was liaising with the council about new housing and families in the enrolment zone.
"For us, it's about trying to manage it when we're unsure as to when these children are coming. The growth just happens and it's about being proactive rather than reactive."
The ministry provides teaching space for in-zone students, who are guaranteed a place at the school. Some schools privately own buildings and classrooms to accommodate out-of-zone students, whom they were not required to take.
The ministry does not hold information on privately owned buildings.
In June, Education Minister Hekia Parata announced three Hawke's Bay schools would get eight extra classrooms at a cost of $4 million - four at Havelock North Primary School and two each for Te Mata School and Lucknow School.
Havelock North and Te Mata schools had been using extra areas such as the library, administration area and music suite to meet the growing enrolment demands.
Nationwide, a growing divide between demand for high and low decile schools was becoming problematic, said the chairman of the NZ Secondary Principals' Council, Allan Vester.
Some parents sent their children to higher-decile schools because they believed the quality of education was higher but he said that was not necessarily true.
"By and large, high-decile schools tend to be getting larger and very low-decile schools seem to be getting smaller.
"That holds true in pretty much any community where there is choice," Mr Vester said.
"From an overall efficiency as a network and use of public money, it would be much better if all schools were seen as great schools and people simply went to the school closest to their house."
Mr Vester, principal of Edgewater College in Auckland, said the vast majority of baby boomers received a good education attending the closest school and developing stigma around a school's decile was not healthy.
"It's a concern. From my perspective, not just as a principal but as a general educator and what's good for the country, I don't think this divide that's growing is good," he said.
The ministry managed the complex school network well but spent a lot of money running rural schools that operated well below capacity.
Schools exceeding ministry-funded capacity in Hawke's Bay:
* Eskdale School, Frasertown School, Greenmeadows School, Havelock North Primary School, Hiruharama School, Irongate School, Kaiti School, Karamu High School, Lytton High School, Mahora School, Makaraka School, Napier Boys' High School, Napier Girls' High School, Napier Intermediate, Parkvale School, Port Ahuriri School, Poukawa School, Pukehamoamoa School, Pukehou School, TKK o Te Wananga Whare Tapere o Takitimu, TKKM o Kawakawa mai Tawhiti, TKKM o Nga Uri A Maui, TKKM o Ngati Kahungunu o Te Wairoa, Whangara School.
* The Ministry of Education could not provide updated school roll numbers. The numbers included in the story were full-time equivalent (FTE) figures.