Let me just start by saying I'm no expert and several people on this board appear to be, so hopefully they will chime in. My DS11 is ADHD and dysgraphic and his WM is 113 and his PS is 103. I believe that having both low WM and PS (the part of IQ that indicates the brain's "executive function") strongly correlates to ADHD. Your son's are lower than his VCI and PRI but nor so low that I would immediately think about ADHD.
OTOH, my DD8 is most assuredly not ADHD and has a somewhat similar score pattern to your DS. Her VCI is 155, WMI 132 and PS 100. What I see over and over on this board is that low PS in gifted kids is not uncommon or concerning. Also what you describe your son doing in class-reading textbooks-is not typical behavior for an ADHD kid.
I am really on a limb with your WJII scores but I notice a pattern of depressed scores regarding tests related to math and writing fluency, math calculation and spelling. These are all areas of extreme struggle for dysgraphic kids so I would say your DS' scores are affected by his dysgraphia.
His reading in class and inattentive behavior could be the result of writing avoidance. Is he allowed to use an Alphasmart or computer? When my son got this accommodation it changed his life!
