The nativity story of Jesus's birth is the origin of Christmas and it is why we celebrate Christmas. Even if you don't believe it there is still a lot of value in learning it as it teaches about history. It also teaches kids to understand what many people believe and have a tolerance for it, even if they don't believe it.
As a teacher I think it is extremely important to teach children about the Christmas Nativity. I am aware that not everyone believes in Christianity, which is why Christianity is not the only religion taught in schools. Children learn about various religious festivals throughout the year from different backgrounds. We expect our children to grow up in a culturally diverse world yet not teach them anything about it? Teaching the Nativity as well as other religious festivals and traditions helps to eradicate ignorance of them and us. This is all one world and we all share it and personally I would rather teach children to grow up to be tolerant and kind towards all people of all religions. So yes we should teach the Christmas Nativity.
Should we not teach how the nazi's killed the Jews because they are a religious group. Even though the text book facts are inaccurate on the Spanish Inquisition and the crusades they are still in history class because they are used to misinform students. The nativity is to hard to corrupt so that is why the religion excuse is used to keep it out of school.
Children should not learn about the nativity in school because it is a religious story. Children should not be forced to learn about a particular religion over another in public schools because there is a separation of church and state. Children can have their own religious freedom but it must be outside of school.
Not everyone believes in Christianity, and if it were to be taught in public schools, that would end up combining church and state. If one religion were to be taught about, all religions should be too, or at least all major religions. It would be unfair to those who don't believe in Christianity as they might feel inferior to those who do. In private schools? Fine. Parents are paying for their students to go to those schools. However, public schools, funded by tax payers in the state who don't all believe in the same religion, should not teach children about the Christmas nativity story unless all religions are also accounted for.