There is a typo here as it should read Royal Wanstead School CCF.
The Wanstead Infant Orphan Asylum changed its name to Royal Wanstead School in 1938. RWS did have a Cadet Corps but no OTC.
Royal Wanstead School CCF did not survive into the 1970s as the charity, that ran the school, closed all of its schools in 1971.
http://royalwanstead.com/rwsstart.htm