Steve piqued my curiosity with his question regarding what would happen if a student took the "guaging and grillz" dress code to court. He received philosophy and recollection at first, but I decided to do a bit of quick research, and this is what I came up with.
First, some background:
Court cases have established that students are entitled to freedom of speech, so long as it doesn't "materially and substantially interfere[s] with the requirements of appropriate discipline in the operation of the school." Further, there is no right to "vulgar, lewd, obscene, and plainly offensive speech." School newspapers, speeches, and flyers are also at the discretion of teachers regarding censorship. The short answer: So long as a school can prove that speech would be even remotely disruptive to the learning of others, it's out. This can include potential violence (such as gang related paraphernalia) or substances illegal to students of that age group.
There seems to be no consensus on speech specifically related to one's own body. Some cases have allowed dress codes banning earrings to be upheld on the basis of gang-related fashions. There are cases which prohibit schools from regulating hair length, but regulation of hair color seems to be acceptable still in some places, though not others.
Sources: Ohio General Assembly, ACLU of North Carolina, First Amendment Center.
With that in mind, Steve's question was, "What if somebody took that school district in Texas to court?"
My crystal ball is broken, and my Magic 8-Ball keeps telling me to ask again later, but I'm guessing that the court would rule in favor of the school district.
I base this on several different factors. The school could argue for the disruptive nature of the fads, as many students will find the self-mutilation of "gauging" to be a bit nauseating, and because of the speech difficulties that "grillz" often cause.
The school could also make some argument towards gang paraphernalia with both of these, though a connection may be hard to establish (and I'm not aware of any myself).
Also, with precedent in mind, if a school is able to regulate hair color, then it seems likely that it can regulate other forms of body modification, which "gauging" would certainly fall under.
I maintain my argument that the law regulates body modification for minors in certain circumstances, though I'm not certain that would play into any judicial ruling.
That's my answer. Hopefully, somebody beside Steve was curious.