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.

It was the intent of the Founding Fathers that the State (our federal government), unlike the States of Europe, not impose any one particular religion on the population. If you know any American history, you will know that groups of people (Puritans, Quakers, Huguenots, Jews) came to the colonies so they could worship in their own way without fear of being arrested, imprisoned or put to death. Regardless of their own religious beliefs, Jefferson and his peers wanted religion free from government control.

The US Supreme Court in subsequent years has interpreted the Establishment Clause to mean that no publicly funded institution (Freshwater’s school, for example) can favor one religion over another. Freshwater was in fact doing exactly that in his sciences classes, as well as being irresponsible with high voltage equipment.

Sure, the phrase “separation of church and state” is not in the Constitution. Neither is “liberty and justice for all,” or “life, liberty and the pursuit of happiness.” What’s your point?