Read this passage from Tinker v. Des Moines Independent Community School District. What is the main purpose of this section of the document?
The school officials banned and sought to punish for a silent,
passive expression of opinion, unaccompanied by any disorder
or disturbance on the part of petitioners. There is here no
evidence whatever of petitioners interference, actual or nascent,
with the schools' work or of collision with the rights of other
students to be secure and to be let alone. Accordingly, this case
does not concern speech or action that intrudes upon the work
of the schools or the rights of other students.