It will be hard but I’d focus on your kids’ different strengths. I have a similar situation - we are in DC, so no issue with AAP vs non-AAP, but one kid did just more academically inclined and is multiple grade levels ahead in math; other kid is very bright, but has adhd and is not multiple levels ahead. I try very hard to focus on their individual strengths. I would try to explain it as, her brother needs some more challenge in some specific area (ideally this is not a subject she’s very into!). Overall, I think the most important thing is to encourage them in their strengths. Siblings without rivalry is a great book for some of these issues.