Councils have paid more than £10 million in compensation to people exposed to asbestos in English schools.
Asbestos is present in more than 12,600 council-run schools, according to figures obtained by BBC Yorkshire.
This number is believed to be higher, with many schools having become academies and not included in the figures.
The National Union of Teachers says up to 300 adults die each year because of exposure to asbestos while at school.
In the last five years local authorities have also recorded 99 instances of significant asbestos disturbances, where people have been put in danger because of potential exposure to the substance.
Asbestos has cancer-causing properties and, if the dust and fibres are inhaled, can lead to serious illnesses including mesothelioma, which doctors are unable to diagnose for many decades after the initial exposure.
The use of asbestos in commercial buildings, such as school buildings, was common until 1999.
Kim Harrison, a specialist asbestos solicitor at Slater and Gordon Lawyers, said: “Sadly we see too many cases involving people who have been diagnosed with mesothelioma as a result of asbestos in the schools they have worked in. It is alarming that this is not a historical issue, but one that is still affecting people today.
“Asbestos is a highly dangerous substance when disturbed. It is not just teachers, caretakers and school employees who are at risk of exposure to asbestos, but also pupils of the school. For those of us with children, it is frightening to think that asbestos is anywhere near the likes of a playground or classroom.”
Rachel Reeves MP, chair of the Asbestos in Schools group, told the BBC: "This is a ticking time bomb because very few teachers and parents know that there is asbestos in schools. The very least we should do is make sure that this information is available to them.”