Just looked and if you Google Goldsmiths school, Steel Cross, Crowborough a number of results may be of assistance/interest. Some records are held in Brighton which might be worth pursuing.
It might also be worth contacting Crowborough town council to see if there is a local history group who may have helpful information/photos of Crowborough.
Also, try East Sussex records office to see if they have any records pertaining to the school and any collections of photos including Crowborough.
Final thought, the school was incorporated into and supported by Goldsmiths so maybe try them too.
An interesting project