My ds has had input from professionals since he was about 10 months old, speech, physio, ot, paeds etc. He has a complex range of needs...physical, medical, developmental etc and had inclusion support, an EHCP, and a place in a complex needs resource base.
We have come cross some amazing individuals who have helped ds, helped us and are like gold dust.
Unfortunately we have also come across many individuals who are like poison, they have questioned our (alright, my) parenting, lied and neglected to support ds.
When ds had an autism assessment (not supported by school) the school lied and said ds had no issues at school so any difficulties with behaviour were as a result of his home life. Ds didn't get a diagnosis, despite many autistic tendencies, as he was 1 point off the cut off score. The consultant said he could see he had "many strong features of autism but they were not consistent in different environments"
A month after the assessment (at 8) he was diagnosed with a rare genetic syndrome which has features of autistic traits and ADHD.
The best support we have had has been from LD CAMHS and portage when ds was younger. CAMHS have been incredible in getting school to understand ds's issues and in providing strategies that support ds and us as a family.
Having a diagnosis has helped, because the few children and young adults around the world with the same syndrome all have similar issues, so school have to accept that unless all of our parenting is at fault, maybe there are other factors at play.
School has been the most difficult, with ds becoming ill due to anxiety, a TA telling us that I hampered ds's development, and telling ds that the supplemental drinks he needed for extra calories were making him sick amongst many many incidents. It got to such a point that dh had to take ds to school as the TA would no longer communicate with me.
I also work with preschool children with disabilities, and see the flipside of professionals and how some of them talk about parents. It is often appalling.