I recall in the second grade in 1937 in Rhode Island, the teacher having us recite the lord’s prayer* each day. I don’t think the teachers in grades, 1,3, & 4 did. And from the fifth grade in 1940 to graduation in 1948, in the Los Angeles public schools there was no mention of religion that I remember.
*It was the one that starts, “Give us our daily bread, , ,”, not the one that starts, “Now I lay me down to sleep. . .” I don’t know which is which. 
Occam