Suburban developments in Stoke and a new highway past Mapua have created demand for at least three new primary school classrooms.
Rolls have grown beyond capacity at Mapua School and Stoke School as a result of roading and housing developments in south Nelson, the Ministry of Education's head of education infrastructure services Kim Shannon said.
Last year the ministry approved the building of two new "roll growth" classrooms at Mapua School to cater for increased enrolment demand, Mrs Shannon said.
One new classroom was also approved for Stoke School, she said.
The roll at Mapua had climbed 25 per cent over five years to 262 in July last year.
"The roll is expected to grow further as a result of improved highway access between Mapua and Nelson and increased property subdivision," Mrs Shannon said.
Principal Neil Chalmers said Mapua School, which operates a zoning scheme to limit enrolments, was responding to rapid suburban growth.
At Stoke School, the roll had increased 40 per cent to 204 students in 2013, she said.
"Student numbers are expected to grow further as a result of increased subdivision in Ngawhatu and Marsden Valley. Development within Stoke village itself has also become more concentrated."
The classrooms at Mapua are expected to open in mid-April, while Stoke School's new building will be officially opened on February 7.
Mrs Shannon said other primary schools in Nelson were also beginning to get "quite full", including Clifton Terrace School and Victory Primary School.
Both schools, as well as Hampton Street and Nelson Central, expressed concerns at a ministry "zoning" proposal that was intended to stem enrolments.
The ministry last week stepped back from its proposal to develop enrolment schemes.
Instead it will now invite the schools' principals to work with it to find alternative solutions to overcrowding issues.
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