My son uses vyvance and it helps him focus. What ever medication u try start with a low dose and work your way up. Work with your provider and let them know how things are going. I went thru a few.. we started with the liquid quillavent then we did stratera but vyvance seems to work well. Aside from appetite loss he is doing great. I just don’t give it to him on the weekends so he can eat. My son other is not on the spectrum but is diagnosed with ADHD.

Okay...so many thoughts. First of all, the diagnosis of Autism in your case does not seem necessary if he is high functioning and keeping up with most subjects in school. The anxiety should be your focus (in my opinion). There are so many SSRIs for anxiety these days. The schools will place him in the correct levels of subjects as needed, with or without a diagnosis.
On the other hand, if you are absolutely determined to nail down ASD as a diagnosis, I would get a third opinion and forget the first group who said "no". Best wishes! :)

Thank you so much! His doctor actually just prescribed Prozac because the Straterra had made him feel so depressed... we picked it up today! I was going to give him a break without medicine, because he seems to be feeling a lot better just from stopping the Straterra, and then start the Prozac soon. Of course I'm nervous because he had a bad reaction to the Straterra, but I really think it will help him overall with his anxiety. Thank you again for your reply :)