As for Smith v. Society of Sisters 1925- there appears to be no such case. It is an Internet myth. It refers to Pierce v. Society of Sisters, which "was an early 20th-century United States Supreme Court decision striking down an Oregon statute that required all children to attend public school. The decision significantly expanded coverage of the Due Process Clause in the Fourteenth Amendment to the United States Constitution to recognize personal civil liberties."
Don't take this the wrong way, I don't want this to come across as me being rude or trying to be mean. I saw that article on almost every Wiccan and Pagan website that has teachers, so you aren't alone in thinking that that was completely true. That's why when i notice not one had actual sources to validate the law, I researched. The beautiful thing about the law is that there's a record of it and it is free and accessible if you know where to look. I use to do senate level advocacy for homeless youth, I learned a few tricks of the trade and when to recognize when more research is needed before making the decision. With children and minors I've learned people often tend to treat them as property and not always give them the right of access to their rights, so I always double check to make sure that I am not selling them short of the respect they deserve, you know?