Hathor,
Thanks for offering a more detailed account of your project. Now that I know more about you and your subject matter, I think I can comment more efficiently.
I have researched. I will do more and I have said I will do more. Why can't people take me at my word?
I believed that you have done research. I also believe that if you're here at AW asking questions about agents and publishers, then your book is extremely far along and possibly ready for submission. But, we really didn't know any details about your project. Whenever a fairly new poster comes in to ask questions, we have to ask more questions to glean more information so we can help you, if that's what you want.
I was asked for more of a description of my book. So here goes:
I won't quote everything you've detailed because that would be redundant in my post here. What you've described sounds interesting and potentially very helpful to other people in your situation, which, according to what I've seen in the news, is quite a few people. So I think your book is needed (not that I've ever doubted it) and I hope you pursue this thing to the end. Actually, I expect you to.
BTW the editor to whom my expert wanted to put in a good word about me is a small press and most assuredly not a vanity one. Assuming that also seemed like a putdown.
This is good to hear. Regarding my earlier comment about vanity presses that seemed like a "putdown," please be assured that my question was a legitimate one. Since I don't know you or your publication savviness, you may or may not be familiar with vanity presses and how to recognize one. We see a LOT of new posters at AW who mention friends having gone through outfits like PA or authorhouse and recommended them. Many people don't know how publishing works. So, my statement to you was a suggestion, possibly a warning, to remind you check on any publisher recommended to you by
anyone, even anyone well-meaning.
In the book, I have lots of legal analysis and lots of citation and quotation of medical and educational authorities. It seems strange to couch what I've done as simply self-help, particularly when the advocacy aspects are extremely strong in the book. I wrote the book to try to change things, not simply to tell the tale of my family.
And it's a noble cause, and many books have been published that try to change things. I understand the point about not telling the tale about your family. So, given what you've said above, the book definitely is not a memoir. It does kind of border on education and not self-help. Tricky. I personally would lean toward education.
I reacted the way I did because I was asked, "Are you an expert?" I was repeatedly dismissed by the local school system and told "research shows" that model X was best for all children -- even though my daughter got A's in model Y and was happy in it, but in model X she was getting D's and was terribly unhappy.
My older sister was in a similar situation with her own son who had to be pulled out of public school because he had some sort of developmental delay in talking. Since he couldn't communicate, he would get frustrated and bite other children. After a LOT of drama and back-and-forth discussions regarding experts and what was right and wrong, and how to properly handle him, my sister had to put him into a different school, got him a special tutor, and was able to get him properly taught. He's 8, now I think. My sister believes he did have early(?) autism and was able to treat it. Perhaps a book like yours could have helped.
Regarding your being an expert in the field, I asked that because it helps when selling a particular book. An agent needs to know your platform because it helps to sell the book to a publisher. (Say, a heart surgeon who writes a book about new methods in treating heart disease. On the flipside, if I wrote a book on treating heart disease based on my limited experience on the subject. The agent gets both proposals and accepts the heart surgeon and rejects mine.)
I've done extensive research on all the issues I raise. (I'm a lawyer by training, so I can research.) . . . I have years of experience as an activist in trying to improve local special education
This tells me your platform is a lawyer and activist. This is good. This information is vital to selling your book to an agent.

And I like how you've vetted your book with so many other professionals. I never doubted your approach, I just didn't know what it was.
I haven't yet seen anything quite like my book and none of my readers have either. What we see are books on different parts of what I get into (this particular disability or that one [although my daughter's labeling kept changing and she defied categorization], special education law, how to advocate for your child, homeschooling, works on inclusion designed for educators, etc.) Then there are a few areas where there is no lay discussion of the issues from my point of view at all (at least I've yet to find them, I haven't finished looking), such as a comprehensive negative analysis of full inclusion (legally, economically, educationally, and philosophically) or the lack of evidence for sensory integration therapy for other than sensory issues.
This tells me there is definitely a niche for this book. You could use most of this paragraph in your proposal to describe how your book is different than all the rest.
Wh
at I've done is written the book that I wish had been available to me as a special needs parent.
This is usually a reason why many people write nonfiction books. I have submitted a proposal to a publisher (on a different subject) for the very same reason.
I guess when I get in the process of research further I may see the need to go to an agent and say explicitly, "My book is genre X." I don't see right now why I can't simply go in and say I have written this book, and describe it. If an agent covers all the types of books my book might be said to be in certain respects, I don't see the problem. Do they have a checklist or something where you have to tell them your book is all in one category? It would seem this would stifle creativity.
You can just query an agent like you've described, provided he represents the nonfiction genres that your book falls into. No, they don't have a "checklist" as you mention, but an agency website will detail what they accept regarding nonfiction. Usually it's more than one genre.
Okay, here's one example. Heidi Lange of Sanford Greenburger Agency. On her page, she states that she represents health, family and parenting, and social issues, among others. I would say that your book would be a good match for query to this agency, because it includes all three aspects.
With all that said, what would you like to know? My unsolicited recommendation is that you try querying a few agents right now and write the proposal. An agent will know that the information in the proposal is subject to change given later rewrites and such. If it would be any help at all, I could share the proposal I wrote for a book I'd like to write on a subject I'm familiar with. One publisher has the proposal now, and I'm waiting for the acceptance or rejection.