Surrey Police is investigating a fire at George Abbot School in Woodruff Avenue, Guildford, which broke out around 12.40pm yesterday (19 November).
Fire crews are reviewing the scene to ensure it is safe before a forensic examination can be carried out.
A statement from the force says: “Our investigation remains ongoing and we would ask people not to speculate as to the cause of the fire until all our enquiries have been completed.
“The rest of the school remains open and we will continue to work with staff at the school while further enquiries are carried out.
“Anyone with any information is asked to contact us on 101, quoting reference number PR/P18277533. Alternatively, if you do not wish to leave your name, call the independent charity Crimestoppers on 0800 555 111.