Links Academy, in St Albans, has been added to the list of schools containing concrete that is prone to crumbling.
The school on Hixberry Lane has been added to the UK Government's list of educational institutes containing RAAC (Reinforced Autoclaved Aerated Concrete).
All pupils at the school continue to receive face-to-face education.
Bushey and Oxhey Infant School, Broxbourne's Churchfield CofE Academy and Watford Grammar School for Boys all join Links Academy on the list.
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...
"...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."
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A spokesperson for the Department for Education added: "Every setting (school) on today’s list has already been assigned one of a team of 80 case workers plus project directors working with schools on the ground.
"Ten regional directors, alongside their teams who know local communities best, are also supporting local schools and responsible bodies.
"This includes providing short term accommodation options and putting structural solutions in place."
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