What is Substantial Disruption?

Legal Definition
The substantial disruption test is a criterion set forth by the United States Supreme Court, in the leading case of: Tinker v. Des Moines Independent Community School District, [393 U.S. 503 (1969)]. The test is used to determine whether an act by a U.S. public school official (State actor) has abridged a student's constitutionally protected First Amendment rights of free speech.

The test, as set forth in the Tinker opinion, asks the question: Did the speech or expression of the student “materially and substantially interfere with the requirements of appropriate discipline in the operation of the school?"
-- Wikipedia