Principal Jo Wilson tearfully described their deaths as "horrible" news which had come as a blow to the close-knit community.
She said she had spoken to Bradley and Ellen's mother Katharine Webb - who fled the family home when the shootings took place.
"She's going to let us know when she's sorted everything out, what she wants the school to do [as a tribute]," Ms Wilson said. "We will be doing something for them but we want to talk together [with Ms Webb] and see what we can do."
The school had been open throughout the day to offer support for pupils and parents, and had received help from the Ministry of Education and police.
"Really, it's a matter of one day at a time now so we can see what everybody needs," Ms Wilson said.
At the scene of the shootings people were paying their respects to the murdered children, and flowers were left outside their Kiwi St house yesterday.
Sensible Sentencing Trust spokeswoman Ruth Money said Bradley and Ellen's deaths were "totally avoidable".
"It is another tragic tragic case of protection orders being merely pieces of paper and the courts letting the public down when people breach them."