Don't jump to conclusions. Acknowledge the problem. In some communities, residents and officials are afraid to admit that there is a gang problem. Some people are even afraid that by giving the problem any attention, they will be encouraging gangs, by giving them the notoriety they seek. All of these concerns should be addressed, and all can be satisfied.
Denial is never beneficial.
You cannot solve a problem until you admit that it exists. Assess the problem. Before you can begin to find solutions to your own situation, you must understand it. To gather this information, you must establish cooperative relations among schools, police, and community organizations. Act on the problem.