How can I prevent a fine against me for my 15 year old getting a ticket for fighting?

My son got in a fight; the other kid pushed him, my son drew blood then got ticketed and suspended and the boy did not. I was never contacted by the school regarding this. I never spoke to a principal or officer. This was his first time to get ticketed for fighting. I received a letter in the mail that we were supposed to appear in court. I am not sure what is about to happen, or what to expect. I have never been through this before. I don't want to be charged a fine when this was my son who acted wrong. I have done many things to get my son help with his problems, even as much as putting him in military school- coming up. There are so many more parts to this story; from runaway to treatment centers to psychologists and psychiatrists, to truancy and community service. I have called the police myself to get him to straighten out. I just don't know what else to do. Now this ticket. I don't want to be charged for the mess he is causing when I have tried countless times to fix things.