If one teaches non jews children in a classroom setting may she teach about different customs that Christians do i.e. bunny’s and eggs easter time, church and Santa on x-mas if her job depends on it?
If the curriculum gives a general overview of different religions and their basic practices there would seem to be room for leniency, when one’s job depends on it. However from your question it seems to be a more detailed lesson in Christian practice. While according to some opinions non Jews may practice this religion, a Jew may not engage in it’s study and teaching even for the sake of livelihood.