There was an interesting survey by the Pew Institute which found that atheists and agnostics scored higher than any other group in their knowledge of religion. I took their 15 question sample test (the test that the survey is based on contained 32 questions). I scored 14 out of 15 correct, for 97.3%.
I don’t think it should be any surprise that atheists and agnostics are the most knowledge about religion, since most of us started out exposed to some kind of religion and came to our atheism/agnosticism through careful study and thought, so it makes sense that we would know more about religion because we have actively studied it.
Mormons came in second, which again makes sense, because many the Mormons have a very big emphasis on evangelicalism. In fact, Mormons and Christian evangelicals were the two most knowledgeable groups about Christianity. If you are going to go out and try to convert others it helps to know your religion and the religion of those you plan on converting.
Those religions that put a bigger emphasis on the actual religious organization, such as mainstream Protestants and Catholics scored lowest. Being raised Catholic, I can tell you that there isn’t much emphasis put on actually studying religion. It’s more towing the party line.
Personally, I feel that world religions should be taught in every elementary school in the country. The more exposure children have to different faiths the more tolerant and understanding they will tend to be. It also benefits them when they get older because then they can make their own choices as to what faith (or not) to follow. A belief that is arrived at by thought and conscience choice is much more meaningful that one that is foisted upon you. It is important to know why you believe, not just what you believe. Understanding why you believe something gives it a very deep and important meaning.