Do you have a therapist or counselor that can act as a neutral third-party with your ex? I'm trying to think of ways to place your child's needs and interests ahead of the interpersonal issues that lie between the two of you.
I know that one of the goals of most divorce proceedings here (N. America) is that co-parents learn to be a functional team-- and courts regularly mandate counseling to help ex-spouses get to that place.
Occasionally, when a situation is so rancorous that the child(ren)'s needs are getting lost in the combative/confrontational/oppositional interactions between parents, a child-advocate is even used so that parents can work through issues of importance without losing sight of who should be considered first in those discussions.
If you can, I encourage you to go that route because this is likely to be far from the LAST time something like this comes up with an HG+ child like yours. The educational system isn't intended for them, and so you may only have a series of temporary "good enough" solutions-- and require vigilant tweaking on an almost continuous basis. Good communication which is functional MUST become a high priority for both parents.
