I was aware of this study of French parenting a few years ago. As a parent educator, I have noticed many parents, struggling with their childrens’ behaviors, who want to “fix” the child rather than look at their own parenting behaviors. This is not to say there aren’t sometimes biological and even heredity causes, but even if this is the case, parents can complicate or work with a situation in the way they parent.
http://www.psychologytoday.com/blog/suffer-the-children/201203/why-french-kids-dont-have-adhd