Reduced deliveries by New Zealand Post have affected board-of-trustee elections, School Trustees Association says.
New Zealand Post cut deliveries to three days a week last year, because of falling mail volume.
More than half of the country's schools held board elections earlier this month.
The association's president Lorraine Kerr said it had complaints from some parents and returning officers about voting papers not being delivered, or only one set arriving in a two-parent house.
The association would be reviewing its processes, she said.
"[We will] look at what went well, but equally look at what didn't go well and what we need to learn from that and how we mitigate it. From the New Zealand Post perspective, gosh that's a huge conversation we will need to have because this will happen again in three years."
The Ministry of Education said 24 schools had been granted extensions for reasons including missed timeframes and postal constraints.
It also said some households got the wrong number of voting forms.
"We are also aware of schools where the electoral roll processing has meant that the correct numbers of voting forms have not been delivered to households."
But Principals' Federation president Iain Taylor was not aware of any problems.
"I haven't actually heard too many negative things actually about the election and even the whole thing about the postage has surprised me actually," he said.
"Obviously different communities [and] different schools have different challenges in getting a confident board, but as we know there's not many schools that haven't got a board so it's obviously been OK so to speak."
New Zealand Post said it was in the process of checking if any complaints were made and was open to discussion on the matter.
"New Zealand Post would be more than happy to discuss and provide advice on postal timeframes for future elections with the School Trustees Association and the Ministry of Education," it said.
"We would also be happy to be involved in any review of the regulations around the running of these elections."