The Encyclopedia Americana says: “The flag, like the cross, is sacred.” The flag is the symbol of the State. Therefore, bowing down to it or saluting it is a religious ceremony that gives reverence to the State.
Given that the pledge of allegiance to the country or to the flag is virtually a religious expression, it should be obvious that such action would be in conflict with those who believe allegiance only belongs to God.
In 1943 the Supreme Court ruled in the West Virginia State Board of Education v. Barnette case that public school students are not required to say the Pledge, concluding that “compulsory unification of opinion” violates the First Amendment. In a later opinion, the Court held that students are also not required to stand for the Pledge.