A blaze which destroyed a primary school is being treated as arson, the fire service has said.
Derbyshire Fire and Rescue Service was called to St Mary's Voluntary Academy in Derby on Saturday, but crews could not save the school building.
Forty-eight hours later there was another blaze at Ravensdale Infant School in nearby Mickleover.
Derbyshire's chief fire officer Gavin Tomlinson said he was "angered to hear both fires were started deliberately".
"Unnecessary distress has been imposed on the children attending those schools, their parents and the teaching staff who work tirelessly to provide our children with the education they are entitled to," he said.
Fire investigators believe the cause of the blaze at St Mary's was "the introduction of a naked flame".
They previously confirmed that the fire at Ravensdale - which is less than five miles away - was started deliberately.
Derbyshire Police is looking into both fires, but they are currently not being linked.
Supt Sarah McAughtie told BBC Radio Derby: "At the moment we're treating it as separate investigations.
"It's wrong for us to jump to a conclusion. Should there be links we'll obviously link them."
Both fires come after a blaze which ripped through Harrington Junior School in Derbyshire in May.
None of the schools had sprinkler systems, which are not mandatory in England.
National Fire Chiefs Council chair Roy Wilsher said: "All new schools - and those undergoing refurbishment - should have automatic fire suppression systems fitted.
"Sprinklers in schools is clearly a move in the right direction."
A Department for Education spokeswoman said: "Where sprinklers are considered necessary to protect pupils and staff, they must be installed."