Why is the religion of scientology allowed to be taught in public schools?:
There are Scientology schools, where most kids who were born into it go, but I have never heard of it being taught in public school.  You wouldn't attend these schools unless you were a Scientologist though, thankfully.  Scientology has kind of seeped into many aspects of society by way of a number of front groups that do various things for the community, like Narconon and the like.  These groups do not advertise that they are really Scientologists, so it is very possible that if you heard that Scientology was being taught in ____ school, it's definitely run by Scientologists.