Schools should not let children touch or try on wartime helmets and gas masks as they may contain asbestos, says updated advice.
Instead they should be double-bagged and destroyed or made safe if they are not clearly shown to be asbestos free, says the Health and Safety Executive.
Teachers are increasingly using wartime artefacts in the run-up to the World War One centenary later this year.
Historians say destroying these relics would be "a disaster".
The Health and Safety Executive (HSE) says it analysed a number of vintage helmets and gas masks at the request of the Department for Education (DfE).
The analysis showed that the majority of the masks did contain asbestos, often the more dangerous crocidolite, or blue asbestos.
Only a minority were asbestos free and it was difficult to tell just by looking at a mask whether it was safe or not, said the researchers.
The HSE also consulted the Imperial War Museums (IWM) about their policies on gas masks and on World War One British Army helmets known as Brodie helmets.
The IWM say they advised the HSE "that all gas masks of any vintage as well as all Brodie helmets should be assumed to contain asbestos, and potentially other toxic or hazardous materials".
"They should not be worn, and people should refer to the guidance supplied by the HSE for advice on how to remove and safely dispose of these items," said the IWM in a statement.
Some of them will be in very poor condition, schools are warned.
The IWM said that the majority of World War One Brodie helmets contain chrysotile or white asbestos in the lining.
Schools with these items in their collections are advised to remove them from use, double-bag them and send them for licensed disposal or to be made safe by a licensed contractor or arrange to have them displayed in a sealed cabinet.
Paula Keating of the Historical Association said schools should not panic and should avoid destroying these objects.
"We just feel that this would be a disaster. These are historical artefacts.
"In the same way that you would not hand a child a hand grenade from World War One but you might give them a deactivated one," she said.
Ms Keating suggested that schools and museums should group together to send the objects to licensed contractors to have the asbestos removed.
"We all know the dangers of asbestos but it can be removed without wrecking the history.
"It would be really sad when we are spending half our lives trying to preserve these things to see them destroyed when there is a better way."
The HSE said the advice did not encourage the thoughtless destruction of items of historical significance.
"We have not told schools to destroy all artefacts. Schools have options, if they wish to retain items they must be stored or kept safely, just as they would be in museums.
"Schools can make masks and helmets safe to be handled or put them on display as alternatives to removing them from classroom use," said a spokeswoman.