I was talking to my 40+ year and still teaching 6th grade mom about this thread. She said that in her county some of the holiday decisions were based around liability issues, costumes, easter eggs, candy, just became too problematic. Their winter holiday has Santa, but nothing religious as she teaches at a pretty diverse school. Easter they do another spring fair, instead of carnival.
Some of the liability issues regarding Halloween came from costumes being too long, or unweldy, and kids getting hurt, she said the worst thing that ever happened was a broken arm from tripping on a long hem. Not a huge deal, but still, more risk. They got rid of candy being brought in by parents/students and now supply it because of allergies issues (she now gives her kids jolly ranchers, sour patch kids, swedish fish, etc., basically candy which has no dairy/nuts and is gluten free/vegan, she has a larger list though those are just ones I see her buy the most often), no hay rides or hay in the school because of allergies, but they have games with prizes like halloween/fall pencils with crazy erasers, sticky hands, tattoos, etc. Easter is pretty much the same as a spring fair. Their Winter celebration has been more frosty/snow themed for a long time. I thought that all seemed very rational and inclusive, and still pretty fun.
She also teaches, or has (same school since 1991), when the school went peanut free when a child had a serious peanut issue. I don't think that's the case right now, just when the kid who had life threatening allergy was enrolled.
ETA: Mom doesn't live in a progressive state, and lord, she teaches out in the country. The parents have been shockingly good about wanting to include everyone, in holidays and I know when the school had to do away with peanuts the teachers were concerned it might cause problems. Nope, apparently, the other parents were fantastic and would do everything they could to make sure that little girl was safe. They also came up with funny dress up, but no costumes, for the week of Halloween. They have to be within dress code and no distracting accessories, like wings, no face covering, no hoodies pulled up (hoodies are fine but faces must be visible is a regular rule).
Another addition and I'll shut up! Mom also said for a while the kids could change into the costumes at school and that "a nightmare." She was done talking then. I think she was having flashbacks or something.