The first amendment reads "Congress shall make no law respecting an establishment of religion o prohibiting the free exercise thereof"
Modern judges interpret this as preventing bible reading in school, prayer at school assemblies, creches on town property, ten commandment monuments in courthouses and other rulings that have given offense to many good citizens.
In actual fact, the establishment clause says no such thing. Establishment of religion means the sort of deal King Henry VIII gave the English church, namely, you churchmen all work for me, the king, and you no longer work for the pope. After a controversial attempt to return England to Catholicism, it was required that all English kings and high officials be members of the Church of England. Catholics, Quakers, Puritans and Presbyterians need not apply. The Church of England was "established", the dissenters were out in the cold. In fact, belonging to these unestablished dissenting churches was a reputation destroyer, as bad as belonging to the communist party in current day America.
Dissenters set up colonies in North America, Puritans in Massachusetts, Quakers in Pennsylvania, Catholics in Maryland. Lots of Presbyterians came over too but didn't set up a special colony for themselves.
Naturally when the Constitution was written, each American church feared that one of their competitors might become "established" with all the benefits and perks that the Church of England enjoyed back in England. And so, a compromise was placed into the Constitution, namely that no church could be established.
This compromise worked very well up until the 1960's when judges highly trained in nit picking and ignorant of American history decided that "establishment of religion" meant any religious expression.
Today the TV is alive with stories of a federal judge ruling that a national day of prayer (how harmless can that be?) is unconstitutional.
The country would be better off if law school required two credits of American history for graduation. Morison and Commager would be a good text.