A 26% decline in the number of pupils being home-schooled in Otago during the past decade has left home-schooling organisations scratching their heads about what is behind the decline.
Ministry of Education statistics show the number of Otago pupils being home-schooled had decreased from 158 in 2005, to 117 in 2014.
Elsewhere in New Zealand figures remained relatively stable overall.
Home Education Foundation spokeswoman Barbara Smith, of Palmerston North, was surprised by the decline in Otago numbers.
''I've got no idea what could have happened.''
Sometimes when a support group changed around and a vital support person left the community, it could have an effect, she said.
The opening of a private school could also have an impact because parents sent their children there.
But that was not the case in Otago and the precise reason for the region's decline was not known, she said.
''There might be the same amount of people still applying for exemption certificates, but there might have been a bulk amount of people [from Otago] just go off for some reason.
''It's a very hard question to answer, that one.
''We don't know why. There's no obvious reason why that is happing.''
However, Kiwi Families parenting support group director Rochelle Gribble, of Wellington, believed Otago's rural population might be contributing to the decline.
She said Otago had a large rural population, and believed there had been a general shift away from home-schooling by rural families.
''People who are more isolated and rural are more likely to want to send their children to school because there's more contact - there's not 10 families around the road like there would be in a city or town.
''It's much harder for rural and isolated families to home-school because they don't have a social network and there aren't other home-schooling families around to do stuff with.''
Ms Gribble said the overall decline in the school-age population in Otago was also a factor.
Under the Education Act 1989, all New Zealand children have the right to an education.
Sections 20 and 25 of the Act state children aged 6 to 16 must be enrolled at, and attending, a registered school whenever it is open.
However, parents and guardians may apply for a certificate of exemption from enrolment at a registered school for their child under section 21 of the Act.
The Act states: ''Children must be taught at least as regularly and well as in a registered school, or in the case of a person who would otherwise be likely to need special education, will be taught at least as regularly and well as in a special class or clinic or by a special service''.
The Ministry of Education must be satisfied of this before issuing a certificate of exemption from enrolment in a registered school.
The reasons for choosing home-schooling are complex, but many parents do it to have a closer relationship with their child, for religious reasons, or because they have a child with special needs.
Other reasons may include having more control over their child's education, or parents' concerns about the teaching offered by registered schools.
