Four year groups - all of Key Stage 2 - at Ash Green Primary School in Mixenden have been left without classrooms after the fire at the school's upper site on Clough Lane last night.
Headteacher Mungo Sheppard said: "We're absolutely devastated for the children and community and staff but we're incredibly positive, as always.
"We've had amazing support from the emergency services and council.
"We're just absolutely determined to get children back in the building up here."
He said the fire destroyed between a quarter and a fifth of the upper school building. The Key Stage 2 block - with classrooms for Year 3 to Year 6 - has "gone".
He is at the site today working with other agencies to determine the extent of smoke and water damage to the rest of the building and reconnect utilities.
There are several options for where children can be taught for the next two weeks before the half-term break, he said, including looking at accommodating them at the school's other site.
He has also had offers of support from other schools across Calderdale but he is keen to keep his pupils in Mixenden, if possible.
"We've been inundated with support from other schools to house our children and of resources," said Mr Sheppard.
"I'm massively grateful for that but where we can, we want to try to educate out children in Mixenden at Ash Green."
He said the outpouring of support seen for the school has been "fantastic".
"It's wonderful," he added.
Read all our live updates as the investigation and recovery starts after the fire HERE