Hi, and welcome.
I'm short on time... so forgive me if this sounds abupt, not trying to be...
Anger problems in a teen/tween male? High chance of depression. It comes out as anger, rather than "down".
Where does the depression come from? Either it's classical depression, OR... it's secondary, related to not having real needs met over a long period of time. Not because you're doing anything wrong - but because of missing dxes, OR because school isn't handling his current dxes correctly.
ADHD is an unusual diagnosis. It is REAL - don't get me wrong. (I have it...) But, it rarely stands alone (although it can, my K2 is that way). Usually, a kid with ADHD has other things going on, too:
1) half of all kids with ADHD have Developmental Coordination Disorder (DCD) (developmental coordination disorder, a motor skills issue)
2) many kids with ADHD have LDs - dyslexia, dysgraphia, dyscalcula, and others
3) something like 70% of kids with "ADHD plus a Learning Disability (LD)"... have Auditory Processing Disorders (APD) - auditory processing disorder.
And that's just the ones I know off the top of my head.
ADHD is also unusual in that it can be given as a diagnosis when the real diagnosis is something else. Other things DO "look like" ADHD. There's an article just posted on the news section about confusion between ADHD and Obsessive Compulsive Disorder (OCD). There can be confusion between ADHD and Auditory Processing Disorders (APD) (it's possible to have Auditory Processing Disorders (APD) and not have ADHD...) And many kids who start out with an ADHD diagnosis are actually Aspie/Autism Spectrum Disorders (ASD), or bi-polar, or other things.
In the mean time, yes, being 12 does complicate things. Puberty does wonders to medication effectiveness, as does the massive growth spurts that go with it (been there done that).
So... it could be any of the above.
Has he ever had a comprehensive evaluation?
Who gave the ADHD diagnosis?
What was he like as a baby, and as a toddler?
Any dxes that run in the family?
Is he adopted?