No, there’s no legal requirements to say the pledge or anything. I’ve never seen it done outside of schools, it’s just a weird tradition that has been carried on.
In my high school nobody in my classes actually said it, but one of the teachers or the student council president would say it over the intercom (we didn’t even stand for it, usually just went back to our work while they talked).
As a younger child in elementary school I remember we were expected to say it, and I do remember a couple kids getting yelled at for not saying it (by the teacher, I don’t think there was any formal punishment). I know some Muslim children would say the whole thing and leave out the “under God” part.
I never paid much attention to it until I got older and realized how weird it was. I’m hoping it goes away eventually.