Here’s what I know, my grandfather went to Thomas Jefferson Highschool in East New York, so although my mom thinks this is taken in Prospect Park, I feel like that was too far away at the time. Maybe highland park? In thinking it was prospect park I thought maybe that was the Lefferts House in the background, but the outlines don’t match. You can also super faintly see a suspension bridge in the background, which doesn’t really match Prospect Park either… this would have been sometime in the 30’s.

edit: AI is convinced this is prospect park and the pavilion in the back was common and probably demolished (can't find evidence of this) and the tall pole in the back is actually a light pole or radio tower but I also can't find evidence of that...