In addition to that.... they also didn't want another Church of England. The amendment prevents Congress from creating a government endorsed religion.
"Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof"
How people took that to mean that there should be ZERO religion in schools or government is beyond me. I really think "Separation of Church and State" has to be the most misunderstood part of the Constitution. Probably more than "freedom of speech," which interestingly enough is part of the same damn amendment.