Principal Bernadette Newlands said the six-classroom school's roll had increased from 123 in March last year to 144 this year - a rise of 17%.
The roll hike was not yet putting strain on the school's resources, but as new entrants started throughout the year, the roll was expected to continue climbing past 150, she said.
"Class sizes are getting up to 32 kids in senior classes.
"But we're managing to keep junior classes down to 17 per room."
Having more than 150 pupils would entitle the school to an extra teacher from the Ministry of Education, but more room would be needed to accommodate the pupils.
The ministry had encouraged the school to start using its library as a classroom, but Ms Newlands said that was not an option.
"The library is core to the operations of the school. We couldn't operate without a library."
So, the board of trustees was now investigating "creative ways to create extra space" in the school, which included the possibility of siting a new or recycled prefabricated building put on school grounds, she said.
While the rolls at many Dunedin schools have been declining during the past five years, Ms Newlands believed Macandrew Bay School's roll was increasing because of the large influx of immigrants into the community - particularly from the United Kingdom.
"About 25% of our school roll is pupils who have come from overseas.
"Plus, there are a lot of kids who had parents or grandparents at the school.
"There's a family connection."
Although the school had good teachers and learning programmes, Ms Newlands said the atmosphere of the local community played the biggest part in the school's popularity.
"I think they come here because Macandrew Bay is a highly attractive area.
"You have a rural feeling with all the amenities of a village, and it's only 10 minutes from town."
