Religion is an important part of the world. It is also an important part of many people's lives. To understand the world, and the different people living here, understanding of religion is important. In my opinion a religions class should be mandatory, at least in elementary school. However, the ones teaching the class and setting up the curriculum has to be unbiased. Kids should not be taught religion, they should learn about them. Just as one learns about history.
Teaching kids that muslims, jews and christians are in fact pretty similar, is important for the development of the world. It will help breed tolerance for different people, and reduce xenophobia.