Why can the Ten Commandments be displayed in a classroom for children of any religion?
The Ten Commandments can be displayed in a classroom because their basic laws and rules simply establish a good society, rather than demanding that a Jewish, Muslim, or any other child accept a particular set of religious teachings. They apply regardless of the child's religion, even if pagan, and societies that rebel against these tenets fall into trouble.
Les explains that displaying the Ten Commandments is not demanding that a Jewish child follow a particular set of teachings, or that a Muslim child do so, because regardless of their religion—even pagan—the basic laws or rules of the Ten Commandments simply establish a good society. When a society rebels against those tenets, it is in trouble; empires have fallen one after another because they ignore these basic tenets of God's law. Les also clarifies that being under grace does not mean the Ten Commandments are verboten or cast aside; they are not a criteria for salvation or a set of doctrines, and we are not under them as Israel was under its legalistic priesthood and sacrifice.