Lisa,
I know you're frustrated with the whole system. Keep trying. You are the strongest and best advocate for your difficult child.
I agree with midwest mom, a long-term Residential Treatment Center (RTC) placement could really help turn things around. I called the police several times on difficult child when he was tearing up my home and making threats. It really helped to have the Parent Report to show them each time they came out. I'm not sure how to paste a link in here but if you go to the forums page under FAQ/Board Help the first topic is the Parent Evaluation & Report.
This helped us so much. Social workers, probation officers, Residential Treatment Center (RTC) staff, everyone got a copy and they could see the pattern of behavior get worse and worse. It's hard to overlook when it's all down there in black & white.
It helped me to write it too. I felt better after it was done.
I hope your difficult child gets the help he needs.