I guess the Teacher should read the 1st Amendment.

The First Amendment

In the United States, the religious civil liberties are guaranteed by the First Amendment to the United States Constitution:

The "Establishment Clause," stating that "Congress shall make no law respecting an establishment of religion," is generally read to prohibit the Federal government from establishing a national church ("religion") or excessively involving itself in religion, particularly to the benefit of one religion over another. Following the ratification of the Fourteenth Amendment to the United States Constitution and through the doctrine of incorporation, this restriction is held to be applicable to state governments as well.