I have two autistic children. They are very well behaved! I wasn't looking for an answer for "naughtiness"
My older son was diagnosed at 2.5, he will never live independently (he's 21 now, I still have to walk him to college, he can't go out on his own)
My 16 yo was diagnosed at 8, he also has adhd, inattentive type, so although he's not particularly hyperactive his concentration is basically crap! School weren't bothered about helping him though as he wasn't disruptive, he'd just sit in a daydream, then get in trouble for not doing his work.
After my youngest was diagnosed I realised reading the list if traits was like reading a list of my life. I was finally diagnosed at 44. It answered so many questions about my life - why I struggled at school, especially the transition to secondary (where I had that much trouble I saw a child psychologist there, though as far as I know nothing ever came of it) why I've always struggled in life with jobs, people, anxiety, housework, everyday life.
I wish I'd had a diagnosis as a child, I'd rather that label than the ones I did have - lazy, slow, stupid, unorganised.