Kelly's 1922 Beckenham & Penge street directory lists it as:
St. Christopher's Boys' Home (Society of the Holy Family).
No 5 was a private house in the following 1923 directory and also in the 1917 one. I don't have house-by-house directories for 1918-21 (if any were priduced), and I haven't yet found it elsewhere in the area in any other years,
A Mr Arthur John Summers, solicitor, is shown not far away at 6 Stembridge Road in 1922 qnd 1923. No sign of a Miss Mabe.
I'll keep looking, but it appears it may have been short-lived or moved elsewhere.