The other school, the mysterious South-West London College, has been mentioned on the blog before (http://www.theerrolflynnblog.com/blog/_archives/2010/4/8/4500454.html) I found my way there, it is not too far from Colet Court, a walk of maybe 20 minutes but you can also take a bus.
What I found is this:

And it really made me doubt that this building used to be a school because ALL the buildings around, the whole street in fact, looks like it. All the houses look the same. I honestly doubt that there was enough space for a school, and when you stand in front of it, it is really hard to imagine that there were classrooms behind these walls.
— Inga