Who is that girl?

....from Uncle Bob:
I believe the picture was taken on the roof of the apartment house - most pictures of shots were taken on the apartment house roofs - it had an open space and then most pictures had to be taken in direct sunlight. Dennis has a picture in his office at home which shows the four of us taken on the roof. Will get a copy. The girl I do not know. I know there was three sisters living in the next apartment house which were in the same grade as Ralph and Joe. There is some graduation (from grammar school) pictures of them in a group shot. It could be one of them. I looked at the knickers - it was the custom then to wear knickers until you reached a certain age - then you got long pants - I don't know the age - I thought Ralph was older from the looks of the picture. Was that a collar he had on - or was it a lobster bib!!