This school is located at 1351 42nd Avenue. It is now The Principal Center Collaborative Campus, providing services to youth in the juvenile justice system.
The old front door is behind these "temporary" buildings. That one is labeled "main office".
According to the "Architectural and Historical Resources of the Sunset District:
The Oceanside Neighborhood" published by SPEAK and available in web from at the Western Neighborhoods Project, this was the Francis Scott Key Annex, built in the late 19- teens or 20's, with 12" redwood planks on the upper floor. (Here is the current Francis Scott Key Elementary).
You can imagine it was quite lovely.
Here's a photo from the S.F.P.L. Collection, and the same view today: