Separation of church and state was taken so seriously in my New York City public school that in the line "march into hell for a heavenly cause" from the Man of La Mancha song "The Impossible Dream", one of our teachers replaced "hell" with "fire". I wonder how many kids from Queens were sent into the world confused about popular songs whose lyrics our teachers changed.
When I started school, we learned the Pledge of Allegiance with the phrase "under God". My recollection is that around first or second grade (in the mid-1960s), our teachers told us we couldn't say "under God" any more, due to the separation of church and state (I'm guessing it was due to the Engel v. Vitale case).
When I learned the Pledge, I was too young to understand what I was saying, so I simply memorized it as if it were one long word. When "undergod" was removed, no one taught us kids how to close up the gap, so we silently thought the words "under God", and kept the cadence the same as before.
Some student would invariably screw up and say "under God" out loud, and the teachers would yell at us. As a result, whenever I hear "to the Republic for which it stands" I have a Pavlovian fear response --- I cringe in anticipation that someone will angrily yell at me.