Does the establishment clause prevent schools from promoting religious
doctrine as truth?
Yes, in conjunction with the 14th Amendment to the United States Constitution that gives the First Amendment effect vis-a-vis state and local governments.
The modern notion that the separation of these powers implies
opposition or incompatibility is a gross misrepresentation of the
founders beliefs and intentions, imposed on the nation by a cabal of
hyper-partisan Democrat secularists led by Supreme Court Justice Hugo
Black (a virulent anti-Catholic and one-time member of the Ku Klux
Klan), along with his co-conspirator Lyndon Baines Johnson, author of
the “Johnson Amendment” that purported to ban church involvement in
This is ahistorical bunk from a conservative Evangelical Christian website that doesn't even try to come across as a neutral or unbiased account.
Separation of church and state was a concept well understood and prized at the founding (e.g. by Thomas Jefferson and James Madison), and was incorporated in many state constitutions in the time period during which the federal constitution was viewed as applicable only to the federal government. But, even then the U.S. Constitution had some narrow provisions that were applicable to the states including a ban on religious tests for public office that also applied to state and local governments. Also, most states also separated church and state in their own state constitutions, often in language parallel to the First Amendment, but sometimes stronger.
For example, the parallel provision adopted in Colorado's Bill of Rights when it became a state in 1876 stated:
Section 4. Religious freedom. The free exercise and enjoyment of
religious profession and worship, without discrimination, shall
forever hereafter be guaranteed; and no person shall be denied any
civil or political right, privilege or capacity, on account of his
opinions concerning religion; but the liberty of conscience hereby
secured shall not be construed to dispense with oaths or affirmations,
excuse acts of licentiousness or justify practices inconsistent with
the good order, peace or safety of the state. No person shall be
required to attend or support any ministry or place of worship,
religious sect or denomination against his consent. Nor shall any
preference be given by law to any religious denomination or mode of
The Treaty of Tripoli (1796), for example, made clear that Christians and Muslims were equal and that the government favored neither, and was not a Christian nation. At that time, France (an ally of the United States) was pretty much the only other country in the world without an established national church.
Many of the notable Founders were deists.
In all or most of the Southeast United States. there was never an established church. The last established churches in the United States (in New England, see, e.g. here), were disestablished before the Civil War. The successor denominations to the established churches of New England are the Congregational churches, the United Church of Christ, and the Unitarian Church (which later merged with the Universalist Church, a church which was never an established church but had similar doctrines).
The Bill of Rights eventually started to be applied to state and local governments relying doctrinally on authority granted in the 14th Amendment to the United States Constitution adopted during the Reconstruction era (specifically, in 1868). The incorporation doctrine applying the Bill of Rights to the states via 14th Amendment was first applied in 1897. Portions of the First Amendment had been incorporated not later than 1925. The free exercise clause of the First Amendment was incorporated in 1940. Cantwell v. Connecticut, 310 U.S. 296 (1940). It was all but inevitable that Everson (see below) would be decided that way that it was when it eventually came before the U.S. Supreme Court in 1947, many years before the U.S. Supreme Court made that ruling. Like all major U.S. Supreme Court rulings, this ruling was preceded by lower court rulings reaching the same conclusion.
Black wrote the majority opinion in the 1947 US Supreme Court case
Everson v Board of Education which redefined the separation of church
and state as a barrier to church/state cooperation – reversing over
150 years of legal precedent in which it had been recognized as a
facilitator of church influence in government. It was this early and
egregious example of judicial activism in Everson that shifted America
from following the Judeo-Christian presuppositions of the founders to
the Secular Humanist presuppositions of Cultural Marxism: preventing
government from recognizing the authority of God in our law and
This is also false to the point of being laughable. Everson v. Board of Education (U.S. 1947) followed already well established law and doctrine. There has never been a time in U.S. history after disestablishment in which facilitation of church influence in government was recognized. This is fake history produced by Christian Dominionists to further their own political ends.
This isn't to say that Everson v. Board of Education wasn't an important holding. But, it was not a sharp departure for prior law. It was merely clarification of the details of existing law that was well established in particular stark and quotable terms.
To quote a brief portion of the Atlantic article linked in the question:
The attack on separation began as an attack on a letter by Thomas
Jefferson to the Danbury Baptist Association, dated Jan. 1. 1802.
Jefferson assured the Baptists that "I contemplate with sovereign
reverence that act of the whole American people which declared that
their legislature should 'make no law respecting an establishment of
religion, or prohibiting the free exercise thereof,' thus building a
wall of separation between Church & State." In 1985, then-Justice
William Rehnquist wrote that "unfortunately the Establishment Clause
has been expressly freighted with Jefferson's misleading metaphor for
nearly 40 years."
But this argument ignores a historical fact. It's not Jefferson's
metaphor. Even in 1802, separation was already deeply rooted in
American religious history. In 1644, the American theologian Roger
Williams, founder of the first Baptist congregation in the British New
World, coined the phrase to signify the protection that the church
needed in order to prevent misuse and corruption by political leaders:
"The church of the Jews under the Old Testament in the type and the
church of the Christians under the New Testament in the antitype were
both separate from the world; and when they have opened a gap in the
hedge or wall of separation between the garden of the church and the
wilderness of the world, God hath ever broke down the wall itself,
removed the candlestick, and made his garden a wilderness."
It is this concept--that use by political leaders of religion for
their own ends was a danger both to the faithful and to the peace of
society--that the Constitution embodies. James Madison wrote that
government involvement with the church "implies either that the civil
magistrate is a competent judge of religious truth; or that he may
employ religion as an engine of civil policy. The first is an arrogant
pretension falsified by the contradictory opinions of rulers in all
ages, and throughout the world: the second an unhallowed perversion of
the means of salvation."