Re: Another ADHD post! =)
I haven't read the other posts yet. I don't know the Brown scale. Our pediatrician and school both used the Connor scale. I assume that they're probably fairly similar. These question/answer scales are simply screening tools. They are not meant to be diagnostic. I know a lot of pediatricians are willing to prescribe medications based on just the results of these screening tools. However, I recommend going through the full battery of tests. Request that the school test him for learning disabilities (full battery of testing - speech, OT, PT, etc). Then has the pediatrician to refer you to a developmental psychologist who can perform the rest of the testing.
That way, you really have a good handle on what's going on with your son. It should give a good idea of what your son's capabilities are so that you know whether he will need an IEP in school in addition to cognitive therapy and perhaps meds.