Welcome to the teens! I'm on my second set of teenagers! My twins are 18 years old and will be graduating this June. My first set of kids are 35 & 33 years old and between the two, I have six wonderful grandkids ages 6 months to 13 years old.
First I'd like to say to you that YOU cannot fix the problem, only he can. So the first thing you must do is work on yourself, once you come to a feel good place of acceptance then you can begin to assist him through his adulthood. (this is the hard part! lol)
At 12 yrs old he is now a young adult and making his own life decissions based on the wonderful teachings from you in his childhood. Now he is finding his own way. That's where acceptance comes in! Your role as parent has now changed. You as the parent are no longer in control of his choices. That doesn't mean you have to like or agree with his choices, just that they are his choices.
Communication is very key. Instead of talking to or at him, have him do the talking. Ask thought provoking questions and let him come up with the answers, with guidance of course.
Start with... Son you are becoming an adult and making adult, life changing decisions for your self, as your Mom I can assist you but ultimately, this is your life and you are in charge of it.
Then start asking questions. "Do you think it's a good idea to act up in school?" "What do you think will happen because of your choices" and then let him talk, bite your tonge if you have too! LOL Ask him what he plans to do to correct the issue and what he wants you to do, to assist him.
Put the responsibility back on him. Treat him as a young adult with love and respect, chances are he will start treating others the same.
FYI, my twins still have issues with teachers and school officals, in regards to how they are treated. Some adults treat them like little kids and are very disrespectful, but my twins have learned to stand up for themselves without being rude or disrespectful to others.
You've raised a fine young man J., now step back and let him fine tune himself with your assistance.
Be blessed and be a blessing,