"First Amendment of the U.S. Constitution prohibits officials from from establishing or promoting religion"
"Congress shall pass no law" -- Says nothing about congress, teachers or anyone one else "promoting" religion.
At the time of the adoption of the Constitution, several states had their own established churches. At that time, no court ever adjudicated that those churches were unconstitutional. I read an interesting article by Stanton Evans in Imprimis Magazine - which I kept from that time.
Here is a link to the archive at Hillsdale College, which lays out his case that the current widely-held position on church/state is made up and wrong.