The words "Under god" were not originally in the pledge and never should have been added. The first amendment says, "Congress shall make no law respecting an establishment of religion." God is an establishment of religion. A non-christian should be able to pledge allegiance to this nation without it being under god.
Also, A person that doesn't know what allegiance is and pledges it everyday in school, doesn't even know what they are doing. They should be taught what the word means so they can make their own opinions.