I agree with taking him for an evaluation outside of France, if you can. Doesn't seem like they have a respectful understanding of "differently wired" kids. Sounds like it all considered the parent's job, even if the child is different.
The Connors alone can not diagnose anything. If I were you...you have family in the uk...maybe try there. I don't know how they feel about diagnosing children, but it is certainly in my opinion worth a shot. In the US, he would have no trouble getting diagnosed. France seems to be the most stubborn country I've heard of in that regard. And, yes, I do think it is part of the culture...the philosophy seems to be...kids are what YOU make them. That's so untrue.
And a diagnosis. is not just for the sake of a label. It is so that educators and parents can know how to parent the child. It especially gets touchy in the preteen years. You need to often parent these children differently, but the schools often have to help out too and accomodate. There is more to differently parenting/educating a differently wired child than just medicationi.
It sounds very frustsrating. I'm sorry.