...Legally, what the courts have done is establish a mechanism by which schools can reach outside of the four corners of the school and regulate off-campus behavior.
(1) the court looks for a "nexus" (connection) with the school district. ...we are seeing them permit quite a bit of regulation of the net.
(2) Once the nexus is established, then we run through the traditional student speech analysis.
(a) Is it speech? ... If yes, continue, if no - regulate.
(b) Is it lewd, vulgar, plainly offensive? ...feel comfortable regulating.
(c) Does it promote illegal activities, such as drug use. Yes = regulate. No = continue.
(d) Does it cause a disruption? This is the biggie. There is a lot of legal history here establishing what is and is not a disruption, but the administrator's perception will usually get quite a bit of deference. Typically, if you have a nexus, you probably have a disruption - as the disruption is the nexus...
The effect was to make schools much more proactive in regulating everything related to students.
[Columbine; Bullying and Cyberbullying; Sexual predators & Porn; and other factors],
combined to create an environment where school regulation of off-campus speech was not just allowed by courts ... but it was encouraged by society and school boards.
At some point administrators thought it was their job to regulate off-campus speech....