The two tests that play into the processing speed index are the coding and symbol search ones. Symbol search deals more with visually scanning data although it does require some motor coordination to mark down your response. It, however, is less likely to be impacted by dysgraphia than coding. His coding score is quite low -- well below average which would be a 10. Symbol search is within the typical range. Has he rec'd any OT for his dysgraphia?
If you do go with public high school I'd definitely seek a 504 plan to provide him accommodations so he can perform to his ability. It does sound like his disabilities are standing in the way of performance rather significantly. Since it appears that he'd at least be an average student, the school may not see it that way, but his ACT scores and VCI (verbal index) do speak to a child with much greater potential than average.
