I agree with Miswimmy (Usually do) 12 is a difficult age for boys, for sure...
My ADD was not DX'd until age 43 and it explained SO Much to me. The worst part od ADD is the complete smashing it does to your self-esteem. One way to cope with the complete lack of self-esteem is to Act-Out. Confrontation produces the dopamine our brains crave, it wakes us up from the ADD Fog we live in most of our lives.

Fight for the DX and medication. My life changed within 30 minutes of my first Adderall. Also... It is difficult to accept that you have a "Brain Disorder" and he will likely greive this, so therapy is a must. There is so much opinion out there about ADD that is completely un-founded. This was all I knew about ADD before my own diagnosis.

You should also read as much as you can about ADD, because so many ADD behaviors seem one way, but are in actuallity the opposite of what they appear to be. Most bad ADD behaviors are out of one's own frustration with having poor executive fuction. People tell you to simply "Try Harder" and this is simply NOT possible. The ADDer believes they must be lazy, worthless, becaause all they need to do is just Try Harder.

Stimulant medications are nothing to fear either. The actually do the opposite of what you think they would do. They slow the spinning thoughts down in our brains, making it possible to make better choices. They help screen out the distractions interupting everything you try to do.

Make sure the Psychiatrist is an ADD Specialist.

Good luck!