In Enfield, three schools are affected.
An Enfield Council spokesperson said: “The health and safety of staff and pupils is our top priority and Enfield Council has been working closely with all local schools to identify whether they have been affected by the recent issues with reinforced autoclaved aerated concrete (RAAC).
“We are aware of three schools impacted and can confirm that no schools have had to close. All Enfield schools were able to open for the return of the academic year.
“Winchmore School has identified RAAC in a small part of the school in a changing room and corridor ceiling, between the changing room and the sports hall. This area has been sealed off for some time so there is no danger to staff and pupils.
“St Ignatius College has identified RAAC in different parts of the school but this is also in an area of the school that has been sealed off.
“A third school, Churchfield Primary School, which is part of the Ivy Trust, has surveyors on site identifying whether they may have RAAC.
“The Department for Education is sending surveyors to the school in the next couple of weeks but there is not a specific safety concern at this time.
“Enfield Council is not aware of any other schools in the borough that have been impacted.
“This situation continues to unfold and Enfield Council will continue to work closely with all our local schools to support them as fully as possible through this challenging period.”