Actually this has everything to do with "liberalism" if applied in the behavioral sense, which is what is applied in socialist thinking. And here we have a classic case of stupid laid on top of permissive and mixed with idiocy.
Problem one - they have established a list of hard line rules, which first ban everything relating to THEIR culture, much of it for purely idiological reasons.
Two - they have removed any means of making these hoodlums conform to the rules; classic socialist response to all problems is "ban it". But how?
Three - they have failed to establish or foster a peer environment, where a 'leader' or 'leaders" emerge on their own.
And four - they forgot to whom the classroom belongs, it is not the teacher as the unions like to claim, it is not the students idealists like to claim. It is OUR classroom, we ****ing pay for it.
These hoodlums aren't lost, not at all. The education system, having lost or deliberately surrendered all authority are now trying some theorists idea of a solution.
There are solutions in this. But they are a long way down the line as the brain trust has created an environment where the students see arrogance, authoritarianism, with nothing to back it up. They come from an environment you tell someone to do something you best be prepared to die over it. Why the hell would any of them make any investment in the place, the process and "the dude they sent in here to tell us where to sit our own asses....."
I am no teacher but I have worked the street. The first thing I would have done would have been to read that list of what is NOT allowed, toss it in the basket and start a conversation on why those rules suck ****. Hopefully it will lead to a conversation about self-expression and how that's protected under the constitution, and maybe that will lead to a conversation on how the constitution is working. Ask questions like "What's wrong with wearing gang colors?". May sound like bull****, but there is a lot better chance of getting to them than insisting all the **** they like to do is banned, but no way to enforce it.
But, we are not done in our criticisms. No. The principal refuses to expel anyone! Why is "expel" in there? These are kids who want OUT, and we punish them by giving them what they think they want. First, you have to move off the punishment model and move into a peer setting where the 'rules' will evolve among them based on democratic process
Then I would burn every teaching manual available.