The cost of arson attacks on schools was $6.5 million over the five years to last June, according to the Ministry of Education - a six-fold increase on $1.1 million in the 2003/04 year.
Since then, nearly 60 fires have caused damage to schools. More than two thirds of them were started deliberately.
The cost of fires so far this financial year, including damage at Mangere East Primary School and Kerikeri High School in the past week, has not yet been finalised, although the running total is $3.7 million.
The ministry says about 80% of schools now have partial or total alarm coverage.
It says only 6% of schools have sprinklers and it would cost approximately $500 million to fit them to all schools.
