Hey, Gemini, consider that only NOW you have enough information to be able to make a plan, be able to select a treatment strategy, to be able to talk to the teacher about his situation.

Until the diagnosis, we just could guess or assume it was ADHD. Until then, my son heard everyone say "if you would only pay attention" or "if you would only stay on task and finish your work" or "if only you tried harder, then...". Poor kid! There was no willpower involved, he was not being bad.

Now, this year, if he tells his brain "I have to keep going with math, I cannot think about Star Wars Lego right now!" then a) he has not given in to thinking about only Lego and b) he has a chance to redirect himself BEFORE the teacher points out that he's stopped working, or before the time is up and he's only half done.

You will be the coordinator (appointments with psychiatrist, with therapist, with school counselor, with teacher, with social skills group, etc) and the cheerleader for your son. There are other parents in your area who are doing this too, and it will help to find some of them and ask for their tips!

If you got the evaluation and diagnosis through the school, then you may also want to find a therapist or child psychologist through your health plan so that you can have a professional who is not connected to the school system, more independent and can advise on what services or support to request.
Last tip are my favorite books on ADD - Edward M Hallowell MD wrote SuperParenting for ADD, and a few others that you will enjoy reading, it will help you and the other adults understand a positive approach to guiding your son through school and life. Good luck!!