See Chapter 13: "Blackheath Village & Environs", Vol II, Neil Rhind.
For details of alumni of who served and died in the Boer war, see http://lewishamwarmemorials.wikidot.com/memorial:blackheath-proprietary-school-sa-war-memorial
And the plaque in St Margaret's church, Lee Terrace.
Additional Ref: W. Kirby, B.A., The History of The Blackheath Proprietary School, The Blackheath Press, 1933, Appendix pp. 173-176. Ref:373.222BLA
located in Local History and Archives Centre, 199-201 Lewisham High Street, SE13 6LG
This lists lists 47 alumni who died in WW1.