Absolutely it should, just not one and from a particular viewpoint.
Children should be taught about all religions and not just the popular ones. They should be taught how some are tied together and where they split apart, what the main figures, tenents, and beliefs are, etc. This should also cover the groups within the major religious areas. Don't teach a section just on Christianity, but make sure that it covers the parts and differences from all the off-shoots of it. Cover the different branches of Islam and East Asian religions.
For a lot of people complaining about it not being taught, how much do they know about the Aga Khan or Jainists?
There is so much of a cultural identity, foods, language, and history that is derived from religion.
My point of view, essentially, is that schools are not religious institutions and prayer and individual worship should not be enforced nor encouraged there. But everyone should be learning about a variety of religions, because, well, people are fascinating and beliefs create strong emotions. Who knows, you might even learn more about yourself in the process.