Article VI: “…no religious Test shall ever be required as a Qualification to any Office or public Trust under the United States.”
1st Amendment: “Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; …”
The first isn’t relevant to our question. The second, on a straight reading, means “no official state religion (like those English colonial oppressors have), no government persecution of religion”. Establishment in this case takes its original meaning of the verb “setting-up”, rather than being the noun “building”.
So here’s the question, from a confused foreign observer: how does that make stickers on educational textbooks “unconstitutional”?
“Make no law respecting an establishment of religion” seems to have been replaced by the nebulous concept of “separation of Church and State”, which has then been broadened into “anything any government or state body does which is even concerned with religion is unconstitutional”, and then on to “anything any government, state or otherwise publicly-elected body does which might even be perceived as having something to do with religion is unconstitutional”.
It seems to me that, in over-reaching the claims of the first half of the sentence, the U.S. is in serious danger of violating the second…