Graduating In Peace

I'm not quite sure what this picture represents.  Maybe a prom photo or homecoming.  It's a bit out of focus, but once I blew it up, it looks like the sign above the stage reads Classes with some dates.  I'm not 100% sure, but I'd say 1938, 1939, 1940 and 1941.  Perhaps it means that those four classes raised money to pay for the auditorium.  In any case, there is a photographer's stamp on the back, "ARTHUR W. F. LOWENSTEIN, MORO, ILL. OCT 22 1945"  If I'm reading it correctly, the class of 1941, the last one listed on the sign would have been the last graduating class before World War 2, and the Class of 1946 would be the first to graduate after VJ-Day. 

I couldn't find anything about the photographer, but Moro is near St. Louis, Missouri.