Since many of the people posting here can probably remember what it was like to go to high school decades ago (high school for me would have been in the early 70s), it would be interesting to hear from others about what the gang situation was like back then. I don't recall any problems with gangs, although surely there must have been some. I didn't attend any especially privileged schools, and yet I recall no fear of organized violence in the schools I attended. It would be interesting to know (I have some theories) what happened between the 1960s and now to have made gangs, even among girls, increasingly prevalent. There seems to have been a general coarsening of our culture, a general breakdown in order and mutual respect. Ironically, gangs can provide both, in a perverted way.
Here's a link that may be helpful to you: http://crimeinamerica.net/2010/07/13/female-juvenile-delinquency-doubled-since-1985-while-males-rise-30-percent/