Errr, "this freedom is limited to Congress not making laws restricting speech" was true prior to the passage of the 14th Amendment.  That enforces it on the states, and <i>Morse v. Frederick</i> (<a href="http://en.wikipedia.org/wiki/Bong_Hits_for_Jesus" rel="nofollow">http://en.wikipedia.org/wiki/Bong_Hits_for_Jesus</a>) was based on previous "school speech" jurisprudence.  Schools are a special place and special restrictions are allowed in them, but certainly not total bans on political speech.