Consider expulsion a last resort instead of a quick fix. Mussolini, Hitler and Stalin shared in common that they were expelled from school. Hold in-services on understanding and dealing with childhood and adolescent behavioral disorders. Try to incorporate diverse representation and leadership into the school culture. There is no doubt that violence is expensive.
Clearly violence is bad for business.
Fortunately, there is evidence that certain public programs reduce the odds that children will act violently. Likewise, the city of Boston reports that it had no teens killed by gunfire, for close to a two year period, after they instituted a comprehensive city wide program that included a basketball league for troubled youth and coordination between city funded community centers and churches. Ask your local and state legislators what they are doing to support and implement programs such as these. The community can do many more things than can be listed here. However, it is safe to say that volunteering time is the most important thing one may do to help.