Hi, and welcome.
My kids both started with ADD dxes.
One kid - that has stuck, was definitely accurate, and there is nothing else going on.
The other kid, well...
We ended up with a string of dxes - some later dropped. Including... ODD.
ODD is an "odd" diagnosis in that there are no interventions, accomodations or medications that help with ODD.
Many of us have found that ODD is useful only as a "placeholder" diagnosis.
There is definitely something going on with this kid - the parents aren't just imagining things.
But... until you find out what is really causing the "oppositional" behavior, you won't have many clues on how to handle it.
ADD/ADHD is also an unusual diagnosis in that... it is a fairly common first diagnosis. But frequently, it is either just the first diagnosis, or it's a mis-diagnosis and there is something else really going on.
For example, it isn't uncommon to see ADD/ADHD plus...
1) learning disabilities
2) auditory processing disorders (including auditory figure ground and auditory discrimination, both of which are more subtle than classical auditory processing disorders)
3) developmental coordination disorder or other motor skills issues - fine, gross, or both.
4) mood disorders such as depression and/or anxiety - commonly show up somewhere between middle-school and high-school, when the accumulated effects of missed dxes and missing accommodations/interventions/medications catch up to them
We had all of that and more.
And then... there's the cases where ADD/ADHD is actually something else entirely, like: Aspie, or Autism Spectrum Disorders (ASD), or various other things (that I have less experience with).
Who gave the ADD and ODD dxes?
Has he ever had a comprehensive evaluation?
Our best moves forward came with each new diagnosis.
The more we knew and understood... the better we could respond.
Have you ever read "The Explosive Child" by Ross Greene? It's an alternative approach to handling challenging kids, and many of us have found it helpful on some level.