A 'small trace' of collapse-risk concrete has been found at Exmouth Community College.
Reinforced Autoclaved Aerated Concrete (RAAC) has been found in one small part of the Gipsy Lane site, which is an extension to an older building and affects four Science Laboratories.
In a newsletter to parents, the school said: "We have previously responded to the Department for Education’s (DfE) requests for assessing areas of potential RAAC.
"An update to government guidance late last week has led us to carry out a review and a survey of a small number of areas that had not previously been identified as ‘at risk.'
"In line with the updated guidance, we have informed the DfE and closed this area as a precaution whilst further assessment and actions take place.
"Whilst RAAC is present, our surveyor is content that the building is showing no signs of failure, and therefore whilst we will not use the space there is no immediate danger.
"We are making the necessary changes to student timetables to minimise the impact on learning for students.
"We understand that this may cause some concern, but we would like to reassure you that we have carried out all necessary risk assessments and would not open any part of the school site unless it was safe to do so."
RAAC, or reinforced autoclaved aerated concrete, was used as a cheaper alternative to standard concrete in the construction of public buildings between the 1950s and mid-1990s.
It was only given a safe lifespan of around 30 years. In the 1990s structural safety issues began to emerge and its use was phased out.
Education Secretary Gillian Keegan said: “We are taking a cautious approach so every parent in England can be reassured their child is safe in their school.
“School and local leaders deserve huge credit for making sure the vast majority of settings with confirmed RAAC are continuing to offer pupils face-to-face learning – including all of the 147 schools initially identified two weeks ago.
“We will continue to work closely with affected schools and provide both expert and financial support to minimise disruption and keep staff and children safe.”