Hundreds of students at Coromandel's Whangamata Area School have been evacuated as a "spectacular" blaze tore through the woodwork and metalwork block.
No one was in the block when the fire started on Wednesday morning, but the entire school - which has a roll of about 420 - was evacuated to the playing fields, school administrator Leonie Whittle said.
The fire was still burning when she spoke to NZ Newswire from the office block on the other side of the school.
"There were bright orange flames, it was a real fire," Ms Whittle said.
"It was a bit of excitement, we don't really need it, but no one was hurt."
The school was hosting a sports day and students from three other primary schools were also on the fields and watched firefighters battle the blaze.
School was called off for the rest of the day.
Ms Whittle said the block, built in 1987, was very well equipped and would have been worth millions of dollars.
The Fire Service said six fire engines were called to control the blaze.