A Texas graduation speaker goes off-script to complain about being forced to water down the religious message of his speech, and the school unplugs the microphone. A Florida commencement speaker pauses, and -- fearing a deviation from the prepared text -- his principal stops the speech and has him removed by security guards. An Oklahoma graduation speaker lets loose with an improvised wisecrack using the word "hell," and the school withholds her diploma.Each year around this time, some of America's top high school graduates get an unwanted parting "lesson" from their schools about the limits of the First Amendment.Although the Supreme Court famously told us in 1969 that students do not "shed their constitutional rights to freedom of speech or expression at the schoolhouse gate," the Court's subsequent pronouncement in Hazelwood School District v.