Public schools are funded by all the taxpayers including people of other religions, the non-religious, and atheists. People that say yes to this would assume their religion would be the one taught but if there is even one child that belongs to a different religion, their religion would also have to be taught or else they would be denied their first amendment rights. Some people say that atheism is being taught in public schools but they are wrong. Things like evolution are being taught as theories and not proven fact. Much of the information from the class would come in handy with certain collage courses and some may even require it before allowing enrollment. Question to any that say "Yes" what if your child came home and told you he was taught all about Satan worship? There are people out there who believe in it and if one of their children are in the class, they would have to allow the course.
Because religions are not taught as theories but as believed fact actually degrades the theories. Scientific theories need actual evidence to be even considered as noteworthy but religion requires no evidence at all to be considered fact. To me, that is messed up. How are you going to teach kids about real science when the something that would not even be considered a theory is being taught as fact? Next thing you know, kids will be graduating thinking that the earth is flat an the sun revolves around it because the bible says it's true.