As I have experience on this (I worked at a high school) the best solution is to go for uniforms or dress codes, but one big overall “rule” we have can be described as the “learn not to be a troll or jerk” rule. We would not do a good job as a school if we do not teach students that that kind of behavior will not be approved in the jobs we are preparing our students for. For the simple reason that when it shows up in a working environment it usually ends up with the trolls getting fired or the business having to deal with bad PR or even lawsuits.
In this case the issue was T-shirts with flag designs. What is important here is that some t-shirts that you can see in the OP article were not flags but flag **colored **logos of a martial arts - boxing apparel company.
Looking around it is clear that they have a reputation of having a clientele that is involved in fighting and raising trouble. So much so that when they were more famous (and there was even a gritty reality tv show) that kind of clothing was getting equated with gangs and banned, not only in schools but in bars and pubs as this forum on ultimate fighting - martial arts discusses:
http://forums.sherdog.com/forums/f44/tapout-clothing-banned-pub-1068109/
So I do agree with the decision of the court, those trolls were advertizing something else than just patriotism.
ON PREVIEW:
That connection with violence that TAPOUT clothing had, together with American flag colors (once again, not a flag, but a Tapout logo) is indeed how I would imagine what **Jingoism **is magellan01.