 <unk> similar to the scene staged by St. Francis at Greccio became an annual event throughout Christendom . Abuses and exaggerations in the presentation of mystery plays during the Middle Ages , however , forced the church to prohibit performances during the 15th century . The plays survived outside church walls , however , and three hundred years after the prohibition , German immigrants brought simple forms of the nativity play to America . Some features of the dramas became part of both Catholic and Protestant Christmas services with children often taking the parts of characters in the nativity story . Nativity plays and pageants , culminating in living nativity scenes , eventually entered public schools . Such exhibitions have been challenged on the grounds of separation of church and state . 
