Reading about the rhetorical gymnastics of the Supremes on the Bong Hits 4 Jesus case gives insight into the prohibitionist mindset. As I see it, the fact that the case is being heard at all is a joke. The facts, as I understand them, are clear cut. To sum up: Frederick was, at the time of the 'event' an adult under Alaska law. He was not on school property. The event was not a school sponsored event, merely one for which school had been dismissed. In other words, school was closed. The meaning of the message he displayed is unclear, though obviously provocative.
Here is my take on what happened: The principal, seeing the banner, felt embarassed, failed to maintain her composure, allowed herself to become angry, and lashed out. Upon regaining composure, she realized her error, but by then the 'event' had transpired, so she looked for any excuse for her lapse, cited the 'drug message' as contrary to school policy, and suspended Frederick for 5 days. When he dared to question this, the penalty was doubled. This administrator displayed a dismaying lack of self discipline, and obviously DID restrict the rights of free speech of another adult. She should be fired, not promoted.
If you doubt this position, consider this question: What would the principal have done had one of the adult homeowners across the street from the school unfurled such a banner in front of their own home? What if it had been the son or daughter of such homeowner, standing on their own front lawn, across from the school, with such a banner? Would she have been within her rights to tear that banner down? Of course not. So what difference would it make if they took a few steps forward onto public property? Would that change things? Of course not. What difference does it make if it is a homeowner standing on the public sidewalk adjacent to his property, or another member of the public? Of course, it should not make any difference at all.
As to the discussions between the Supremes, the fact that they are discussing the displaying of signs inside a classroom during class, as if it were a parallel situation when it obviously is not, demonstrates that they are trying to find some pretzel logic way to find in favour of the school. Pity they have allowed themselves to be co-opted by the prohibitionists in power, rather than thinking for themselves. I fully expect them to find in favour of the school, and then watch the free speech limitations increase incrementally.