And this is the heart of it. The Constitution, specifically the First Amendment, was constructed to protect religious expression (the right of conscience, or free exercise) and to prohibit its banishment from the public square. Just the opposite of what we are witnessing now. The intent was to expel from the federal government the predominance of any one Christian denomination over others in the allocation of tax monies or in the granting of other special considerations, so that none would go to any, not to deny all access to the public square. The Founding Fathers never, even for a moment, entertained the peculiar idea that religion (moral instruction) had no place in government, but simply that one denomination could not be favored over the rest.
But a curious thing has happened on the way to the education system becoming the missionary of atheism on the public dole, empowered by the judiciary the parents have started pulling their kids out. Evidently not so much because of the atheism but the teaching of politics and immorality (gay activism) pressuring the children with dont tell your parents, but
Just as in the late Eighteenth Century the people objected to being taxed to support the ministers of a church different than their own, and their children being baptized in a church different from theirs. So religious establishment was denied from the federal government, and was done away with in the states over the first fifty years of the Union.