The room labelled S1 is the following room - without the kids showing, I am sure you have the photo - you can see the pointer to the office shown on the wall on the other side of the hall from inside this room.
That would be here in the church. The red arrow is pointing at the library (S2).
So here is how I went about trying to determine anything about that S1 room. Below are two screen caps with annotations from a drive by video.
As seen there are lights on but they can't be seen through the window right next to it. Perhaps a shade. That said, the room with the dutch doors is where the double windows are to the left in these photos - that room is on the corner of the west and south halls. So the double windows seen on the left in these screen caps must be in any photo of that room. From inside the room a photo toward those windows would show them on the right in the photo. If you can't see that in a photo - and I am going to have to find the original photo you posted because I can't determine much about it with everyone blocked out and blocking other things - then it won't be that room. It can be another room but not that one. So, far I have not found a photo that shows the windows in S1.
The issue with adding more rooms on the south side - not that I wouldn't if I find them - is that S2 is the library. That means that either the library is smaller than I believe it to be and only has 1 window in it. Or there are two rooms that are narrow - 12 feet wide each but can be slightly bigger if the library is smaller - which seems odd but anything is possible in this church. Or there is only S1 and S2 and you have a picture from inside a different room. I can't say without examining the original.
I will find the original and let you know what I can determine about it. At a minimum the paint color is different but they could have painted. That color though has been seen in rooms on the East side of the building in particular.