Why can’t a public school science teacher teach creationism in science class?

It is a violation of separation of church and state.

The First Amendment in the constitution states "Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof."

Usually, in public school, there classes like world religion where they teach more than one religion, like mine. But, creationism is about Christianity, and there are others religions out there, and there are private religious schools for that. Honestly, I shouldn't even have to answer this question, just think about it. Science and religion don't go together, and public schools can't teach about one specific religion because it's PUBLIC!!