My son is 6. He's been with me for 3 years. SID/SPD is a very mis-understood, unknown condition.
Many think that the child is just willful, and needs more discipline. I've had people tell me that a good spanking will cure my son of his touching, moving around, chattering for noise.
I research on the 'net. I print the pages, highlight my son's behaviors - cause/effect. Be knowledgeable. Speak about it confidently, because people will tell you otherwise. I have educated my son's pre-K teacher, his kindergarten teacher, the principal. The kindergarten teacher and principal are special ed - they knew very little of it.
I politely say that, my son has a neurological condition, in which sensory information doesn't get to the right place in his brain - he's not 'being bad' to irritate you.