A fire broke out at De Lucy Primary School in Greenwich completely destroying a mobile classroom on Thursday.
The London Fire Brigade (LFB) raced to the scene at 12.08pm following nine calls about the blaze.
Four engines and around 25 firefighters including crews from Plumstead, Erith, Bexley and East Greenwich, pulled up to the scene on Cookhill Road, Greenwich.
The LFB said in a statement that a single-storey mobile classroom within the grounds of the school was destroyed by fire and part of the external wall of the main school building was also damaged.
The blaze was under control by 1.51pm and an investigation into the cause of the incident is due to take place.