“I thought the phrase was added in the 50’s.”
You are correct in that “under God” was added sometime around then, this article seems to say that this particular school ended the pledge with “God bless America”.
In my school days (albeit long ago now) we never ended with “God bless America”, the pledge ended at the end of the pledge, no more, no less.
If a principal would like to say “God bless America” after the students have recited the pledge I say go for it. If they do not, there really is no problem, as the pledge of allegiance does not have that phrase in it.
This particular instance, is much to do about nothing. Now taken in the wider context of removing God from everything and anything, well that’s a different story.
I tried to argue with twitter rejects that taking God out of schools completely ruined them. I was bashed big time. Go figure.