How does fortas defend the majority decision that free speech in school is constitutionally protected?

Fortas defended the majority decision that free speech in school is constitutionally protected by saying that such an expression isn't disruptive to class. 

Explanation: Abe Fortas was the Supreme Court in 1965 but the position of Chief Justice was denied to him and he had to resign. During his time in the Court Fortas was very concerned about children's and students' rights.

Fortas defended the majority decision that free speech in school is constitutionally protected by saying that such an expression isn't disruptive to class.