What are some considerations under which free speech cannot be considered a protection in a school

The First Amendment to the U.S. Constitution states: “Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press; or the right of the people peaceably to assemble, and to petition the Government for a redress of grievances.”

There are many annotations to this amendment, one of which focuses on Freedom of Expression in Speech and Press, and which is often cited in school law. This annotation can be read in detail here:

http://constitution.findlaw.com/amendment1/annotation06.html#1

What are some considerations under which free speech cannot be considered a protection in a school or educational situation. Give examples and state why.