I am not sure there is such a thing as “milder symptoms”. There is inattentive adhd which is many times described as milder because the child is not hyperactive. It is just as damaging to a child. Many times worse because it can go unnoticed and untreated. Also the age of the child or year is school is also important. Some kids because they are very intelligent can go through high school before the subject matter just gets too difficult. But that doesn’t mean that the anxiety or depression that often accompanies adhd is not there and slowly getting worse.
I agree with all that was said above.