At least in public school system I think it's an "either or" situation. The schools either teach no religion at all, or they have to offer to teach all religions. And as far as I remembered that decision is made by State goverments, not at the federal level.

Not sure about the goverments (local or federal). But according to 1st Amendment, the goverment body itself should be religion-neutral.

The military is different because they always make their own laws, as all other militaries. But US military did pretty well on keeping all religions on the same ground.