Three fire engines and around 20 firefighters were called to a ceiling collapse at a school in Thurlow Park Road in Dulwich.
A ceiling had collapsed on the second floor.
Sixteen people were treated on the scene for minor injuries and 12 children and one adult were taken to hospital by London Ambulance crews. All other children and staff were safely evacuated from the building. Firefighters carried out a systematic search of the building and confirmed with the school that all children and staff were accounted for.
A specialist USAR (Urban Search and Rescue) team and equipment were also used to confirm the building was at no further risk of collapse.
Fire crews from West Norwood and Brixton fire stations attended the incident.
The Brigade was called at 0922 and the incident was over for crews by 1150.