I don't know if anyone has yet answered your question about what are
considered "gang symbols." Symbols vary by city, gang, etc. so it's a
question you'll probably best answer by checking in with gang specialists
(such as a Gang Unit of the police) in your area; I'm sure they have samples
they can show you. Often times, pro sports teams are also taken as a
"personal" team of a gang too, so you might ask about that.
In the area where I currently teach there are three main gangs so it's not
too hard to learn the symbols and logos involved with time and effort.
However, in the greater Los Angeles area there are zillions of different
signs/symbols/logos (well, maybe not that much but LOTS). In an area not too
far from where I am currently, it is much more gang-intensive and in some
cases there can be a different gang every block (yes, EVERY) -- complete
with their own logo and signs. I just learned earlier this year after
spending a day with a Sheriff's deputy who started a community-based patrol
in this neighborhood and visiting some of these more intense areas that
there is not one Crips gang, for example -- there are many many MANY
factions, again sometimes residing next to each other, each with their own
logos and signs. And there is fighting among the factions so signs, etc are
important in identification and territory and all that. Again, it can be
block-by-block gangs in very densely gang-affected areas.
A comment specific to tagging, which someone brought up. Yes, there are
taggers who just tag and are not gang-affiliated. And occasionally a gang
that only tags (i.e., that's it's raison d'etre). However, gangs do indeed
tag. As I mentioned above, it's about territory, staking a claim, so that
anyone who comes into that area knows who "owns" it -- or wants to. Once you
learn the gang signs in a particular area, it's quite clear where areas
under disputes are or struggles for control are -- crossed-out tags of rival
gangs or competing tags, etc.
As someone noted in an earlier email (Lorena Nalin, I think, in her initial
post), displaying of signs/logos can result in violence. And often does
unless you're at a school or place where only one gang is present. And
chances are good that what starts in the school will be finished outside the
school later where there are no rules. So I would fully and completely,
without hesitation, support admin's policy to ban all gang-related
anythings. Kids already have lots of pressure to join; school should be one
place where they don't have to worry about whether or not they are
displaying the right (or any) sign/logo.