The government has been accused of a "callous disregard" for pupils' safety after admitting just 15% of new schools are being built with sprinklers to tackle fires.
Schools minister Nick Gibb said 105 of the 673 schools built and open by February were fitted with sprinklers.
The government said sprinklers were installed when "considered necessary".
But the Fire Brigades Union said the government was showing "utter complacency" on fire safety in schools.
"We've made it clear that newly-built schools and other high-risk buildings should have sprinkler systems," added the FBU.
"Sprinklers can assist in the control of a fire in its early stages, limiting damage and giving occupants additional time to escape, as well as reducing the risks faced by firefighters attending the incident."
Sprinklers are mandatory in new school buildings in Scotland and Wales, but not in England.
Government guidance on safe school design says all new premises should be fitted with sprinklers "except in a few low-risk schools".
There were no fatalities from school fires in the eight years up to 2017/18, but there were 244 casualties, according to official figures.
The National Education Union said it was "perverse" that ministers were not enforcing the advice.
The Department for Education stressed pupil and staff safety was "paramount", and defended its record.
It added: "All new school buildings must be signed-off by an inspector to certify that they meet the requirements of building regulations and where sprinklers are considered necessary, they must be installed."
The new data came in response to a question from Labour MP and former teacher Stephanie Peacock, who said: "The ridiculous thing is that we spend far more rebuilding and repairing schools after fires than we would have paid to install sprinklers in the first place."