Pre-First World War school hall at Southfields (Note the gas lamps).

Jeff Jeffrey adds "The wooden stairs on the right led up to the headmaster's study/office. The teachers in the picture appear to be female, so it was probably the headmistress's study.
The gas lamps were still there in my time (1939), so was the dais and the desk on the left. The headmaster, Mr. Llewellyn, would conduct morning prayers from there. The classes
lined up in their forms facing him. The piano accompaniment for the hymns was played by Mr. Thomas, one of the teachers - a quiet gentleman with nicotine-stained fingers. At the end of
prayers, he would play a rousing march and the boys would march off, form by form, to their classrooms".