Hi B.,
It is so frustrating when you do everything you know to do and it still doesn't work!! You didn't say if you did this or not but did you try to talk to him to find out WHY he's acting out? Sitting down and CALMLY talking with him in a non-confrontational place and manner sometimes will work.
You also didn't say what your belief system is. I believe in God and the Lord Jesus Christ. His Word says that if you ask for wisdom and believe that you will get it from God, he will give you the wisdom you seek. Ask God what to do. The key is that you believe and trust that God WILL give you the answers you are seeking. This should be your first course of action always! Other options include:
*Meeting with his teacher, all 3 of you. That would be a good step to take. You mentioned that nothing has changed at home, but something has set him off somehow. Many times we are blind to small changes.
*Another suggestion, sit down with just you and a trusted friend or family member who will tell you the truth, and ask questions like,
"Have you noticed any changes in my son's life?"
"Is there something I'm doing or not doing that is affecting my son's behavior and attitudes?"
If you do this step, be prepared to hear things you don't want to hear and DO NOT BE DEFENSIVE.
*Have you tried just spending time with him doing something he enjoys? That may sound like a reward for bad behavior, but sometimes kids act out because they aren't getting enough 1 on 1 time with their parents. During this time, they MUST have your undivided attention, and it must show that you WANT to be there with him and enjoying his company. Anything else will backfire on you.
I hope and pray that you will be able to get answers.
T.