In public school kindergarten, we went to school in costume. In Catholic school we didn't dress for Halloween, but there was no condemnation that I remember . . . in one of the early grades, there was an "All Saints Day" pageant & costume contest, celebrated the day
after Halloween. Kids were dressed "as saints." My costume was a full suit of armor (cardboard, cut to shape and spray painted silver) with sword and shield - St. George, of course.
It seemed to be a crowd favorite - parents and older siblings being the crowd, of course. Unfortunately the judges were NUNS
- and they thought otherwise.