Eight fire engines and around 60 firefighters tackled a fire at a school on Kennet Road in Maida Vale.
Part of the roof of the building was alight. One woman was treated on scene by London Ambulance Service crews.
Station Commander Hardeep Dale, who was at the scene, said: "The school was safely evacuated before our crews arrived, and we are working closely with partner agencies to support everyone affected by the incident.
"Road closures remain in place while we work to make the area safe, and we urge the public to avoid the vicinity where possible.
"Firefighters used two of the Brigade’s 32-metre turntable ladders as water towers to tackle the fire from above and bring the situation under control."
The Brigade's Control Officers took the first of five calls to the fire at 1307 and mobilised crews from North Kensington, Paddington, Kensington, West Hampstead, Hammersmith and surrounding fire stations to the scene. The fire was under control by 1441.
The cause of the fire is under investigation.