A fourth Suffolk school has announced it will be partially closed after being constructed with aerated concrete.
More than 100 schools, nurseries and colleges in England have been told by the government to close classrooms and other buildings.
Farlingaye High School near Woodbridge is the fourth school in Suffolk to have received a letter about RAAC in their school.
A letter sent to parents and carers from headteacher Mr P Smith said: "I am sure that you have seen from the recent high profile press coverage that a number of schools have been told by the Department for Education (DfE) to close buildings where RAAC is present.
"Unfortunately, Farlingaye High School is one of the schools locally to be affected by this directive.
"I was only made aware of the requirement to close areas as of 11am this morning (Friday) and as such senior staff are in the process of emergency planning for how best to facilitate the safe return of staff and students to Farlingaye for the start of term.
"There will need to be significant re-rooming of classes and also a creative approach to the use of space to find solutions to add capacity whilst some classrooms are out of action.
"We are in the process of arranging a structural survey which will give an indication of the works needed as soon as possible.
"Please be assured I am committed to the full return of all students for the start of term, and we are doing all we can to ensure that this is the case.
"However due to the nature of the situation there may be a need to slightly delay reopening to allow time to reorganise and respond to this very dynamic situation.
"I will write at the start of next week to offer an update."
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