From the 1st Amend, "shall make no law respecting an establishment of religion," That includes coercion by any school dist to learn it. It is any particular creed, concept, or doctrine, or any general reference to any of them.
" It also prevents the government from prohibiting the free exercise of religion by the citizens."
Free exersise does not include using the coercive powers of govm't to spread, or promote it.