I grew up in Michigan, no it's not a Bible belt thing. Things were just different in the 90's, back then God was a huge respect in schools in general but I'm talking general public schools in the 90's, I'm sure 80's and 70's were just as respectful and fearing of the name of "God" if not more. It probably didn't really start changing until right after my time, since then the country has been devolving. I mean, as I said before, we're having one sided decisions made for the sake of comfort but stripping freedom as it were. I'm confused to why students can't be free to take a Bible into school or wear a cross necklace if someone else can wear a pentagram, etc.
I'm pretty sure I'm older than you and this is just weird to me but on the flip side it let's me get a better understanding of where you are coming from. I dunno, I mean my very small town had like 5 7 churches but outside of the pledge and various optional (and I think outside of regular school hours) bible/prayer groups religion was absent from school... I guess unless you happened to go to one of the religious private schools but those were in "town."
Edit- I think we may have stopped doing the pledge in middle school or junior high as it was called when I attended but I'm almost certain we didn't do it high school either.