Bomb disposal teams were sent to five Sheffield schools to carry out a string of controlled explosions of a potentially hazardous chemical before Christmas, an investigation has found.
Bomb squads were sent out to 600 schools across Britain during October November and December after a Government alert about stocks of 2,4 dinitrophenylhydrazine (DNPH) potentially posing a hazard to pupils.
And the BBC investigation under the Freedom Of Information Act has discovered that disposal teams were called out to five Sheffield schools - including one where the Ministry of Defence were called in twice.
The results revealed that Tapton High School was the first place where the chemical was disposed of on October 31.
Sheffield Springs Academy and All Saints Comprehensive in Granville Road were visited by bomb teams a few days later on November 2 - and officials made a repeat visit to Springs a week later on November 9.
Sheffield Park Academy was also attended on November 2 while Eckington School was visited by bomb teams a week later on November 9.
Bomb teams were also called to ten Doncaster schools and one in Rotherham during the alert.
The warning about stocks of DNPH sparked a flurry of calls to the Army, which carried out hundreds of explosions.
The Department for Education (DfE) said it worked with the Army to support schools with "necessary disposals".
Some schools were criticised for not warning the public about the blasts.
The controlled explosions were carried out between 21 October and 21 December 2016 after schools were advised to check the chemical by the government advisory science service CLEAPSS (Consortium of Local Education Authorities for the Provision of Science Services).
The chemical is sometimes used in chemistry lessons and safe if stored correctly, but dangerous if allowed to dry out.
It is known to pose a risk of explosion by shock, friction or fire and is usually kept inside a larger container holding water.
A government spokesman told the BBC: "We contacted schools last year to remind them of the importance of storing chemicals for practical science activities carefully.
"We've been working with the Armed Forces and the police to support schools with any necessary disposals."