P.S. 24 was once the most visible landmark atop Spuyten Duyvil Hill–being a relatively large building with no other tall buildings around it. This 1930s map shows where it was:
It was a red brick building with a green copper cupola. The building is visible in many old photos and paintings with the hill in the background. In this Ernest Lawson painting, you can see it on the right hand side (the view is from Inwood):
In this Vernon Howe Bailey sketch, you can see it on the left (that’s the Columbia Boathouse in Inwood on the right):
Here is a family photo taken from about the same spot (PS 24 is on the left):
Here is a shot taken from about where the Kennedy Campus is today:
I believe it was torn down in 1940. The students must have had a heck of a view of the city with no tall buildings blocking visibility. I bet they could have seen the Empire State Building being built from the 2nd floor windows.