We had some religion when I was in early grades, now I don't recall what exactly, but there was a time, maybe 1964 or so, when certain items were removed from the display. Nobody paid any attention to whatever it was, maybe they had the 10 C above the chalk board. Maybe the Christian flag was displayed in assembly?
We did pray the Lord's Prayer before basketball games, I recall that distinctly. Our coach led it, nobody much seemed to care.
I was raised a Southern Baptist and they were hard core in support of separation of C&S.