Can a teacher be fired for not participating in certain projects due to her religion?

I need court cases stating that a teacher can or can not be fired for their religious beliefs. The only case I found (Palmer v Board of Ed City of Chicago) states that this teacher was fired due to not teaching about patriotism. My scenario states that a teacher will not recite the Pledge of Allegiance, sing happy birthday or plan gift exchanges during the Christmas Season can she be fired? Please help!!!