In our experience a dx has help significantly. If the school only went with an OHI (other help impairment) with ADHD, we wouldn't be getting all the extra services AND understanding we are getting now. An AS dx has given us an in-home trainer who helps J with learning to focus on getting ready for school in the morning (one of our hardest times of the day), learning time management and other social issues such as empathy, respect, or any other area he is struggling with.
As J has gotten older (almost 10 now) and the kids at school have gotten meaner and more clickish, he now struggles with relationships (keeping friends). The AS dx now provides a counselor to help him learn how to deal with social problems he has been dealing with at school. (i.e., the boys him a funny name and tease him even though they like him, and he misunderstands and literally thinks they are being mean to him, so he says something mean to them and then it escalates from there).
If we had a simply OHI dx, there is no way we would be getting help in these social areas.
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A foolish consistency is the hobgoblin of small minds. ~ Ralph Waldo Emerson