When I went to private school in Pennsylvania and Illinois we never said it. I didn’t learn it until I went to public school in Northern Virginia starting in 4th grade (1998).
I stopped saying it in 10th grade because I think it’s weird to pledge allegiance to my country five days a week. There were a fair amount of students from different countries who simply sat during the pledge. I only had one teacher object to any of this and she was a long term sub for our fashion design teacher (fashion design was an elective at my high school). My friend who was a citizen of the UK brought in the student rights handbook to show her where it stated that students merely had to sit quietly through the pledge, not actually say it.
As an aside this same teacher also wanted us to write letters to soldiers. Nothing against soldiers, but everyone said, “What does that have to do with fashion??” and we never did it.