That judicial second guessing can be both costly and embarrassing. These decisions pit the court against the community. They say society may not establish norms of behavior for minors in a school setting. I don't think that means that if the teacher went over the desk at the child, the language would go unprotected. The teacher certainly wouldn't be protected.
Judicial interference is directed only against public schools.
The Constitution protects from actions by the state. A public school is a state agency. Private schools are not. Judicial interference with public schools discriminates against them in favor of private schools. The refusal of the courts to support society when it tries through law to regulate uncivil conduct in the classroom contributes to a lawless atmosphere.