Kendal School principal Keith Turner announced via Twitter that the Burnside school would close in January 2014.
"Children told but we are being positive so no tears and no long faces. We have our chins up."
Information from the Ministry of Education about the decision would be sent home to parents and caregivers today, he said.
"When we talked to the kids we used that idea that tens of thousands of children move schools every year. We don't want to see children walking out of the school crying."
Turner, who has worked in the education sector for 39 years, planned to retire when the school closed in January 2014.
"We're just naturally really, really disappointed and we're sad to see this happen, but now that we've got the news we've just got to deal with it and move on."
The pupils had been promised "a really good year" and would have a big party to farewell the school.
"We have to try and be as positive about it as possible ... keep things going to give the kids a good deal."
Address: 53 Kendal Ave, Burnside, Christchurch
School type: Contributing (Year 1 to 6), decile 6
Staff: 8 teachers, 10 support staff
Building damage: All six of the school's buildings had some damage, and two will need strengthening work.
Cost: $3.3 million
Land status: Surrounding land is predominantly Cera technical category 1.
Rationale for closure: The high remediation cost, low roll and roll decline, along with the ability for learners to be absorbed by five schools located close by, are key elements behind the proposal to close.