ITA with HK, though I'd be wording it a little different, because I wouldn't allow there to be any question of whether the child is 504-eligible. Rather than hinting at a "misunderstanding" that the child may be eligible, I'd take that as a given, and hint that there has been some form of "miscommunication" regarding its implementation, so if someone can provide advice on the next step in the formal process, so we can move it along, that'd be great.
I mean, you have a formal diagnosis from a qualified professional. Eligibility IS a given. There's no reason for further debate.
