Thanks, Steve. It's your thread so I think you are permitted to go off topic if you want!
The photo certainly confirms my suggestion in reply 18 that the missing right hand side probably mirrored the present day left hand side, but it also shoots down my suggestion that the bricking up of the window might have been done post WW2. Although it's worth noting that in the 1919 photo two windows are bricked up, whereas today the lower window has been opened up.
The backwards hand writing appears to refer to Roof? damage August 1919.
If nothing else, collectively we have come up with a pretty good history of this building from its origins in the 1800 Blind School to the present.