Amendment I

Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press; or the right of the people peaceably to assemble, and to petition the government for a redress of grievances.

The above is the 1^st Amendment. It essentially says that the government shall not pass laws regarding the operations of religious institutions, and that it shall not interfere with the pursuit of religion by Americans. Regarding the 2^nd point, stated another way, the 1^st Amendment essentially says that those who pursue religion, must be able to do so freely, without any interference from the government.

Thomas Jefferson noted in a January 1, 1802, letter, addressed to the Danbury Baptist Association in Connecticut, and published in a Massachusetts newspaper, that the above section of the 1^st Amendment establishes a wall or separation between Church and State. Courts have cited the above letter, to rule that a separation between Church and State exists in the constitution. However, many courts have not bothered to examine the nature of the wall or separation. All the restrictions regarding the separation of Church and State in the 1^st Amendment, are targeted at the state. NO RESTRICTIONS ARE TARGETED AT THE CHURCH. So the wall between Church and State is a one way restriction, which results in the state not being able to touch the Church, but the Church can pretty much do anything it wants (religious-wise) - and the state cannot do anything about it. This means if a kid, for example, wants to lead other kids in prayer in the halls of his school briefly, there is nothing the school can do about it, because the school is an agent of the state, and per the 1^st Amendment, it cannot interfere with the kids’ free exercise of religion. What about a school official leading a religious ceremony? Per the 1^st Amendment, if he is neither passing rules regarding the operations of religious institutions, nor interfering in the free exercise of the religion, he is not in violation of the 1^st Amendment. On the other hand, if the school, which is an agent of the state, tries to stop him, the school would be in violation of the 1^st Amendment, for interfering with his free exercise of religion.

So again, the 1^st Amendment puts restrictions on the state, but none on religion, and further prevents the state itself, from putting restrictions on religion. This is the nature of the wall or separation between Church and State. (See here for historical background information and events, as well as reasonings, that lead to the development of the 1^st Amendment.)