Over time, generationally, it is perhaps not surprising that there has been an increase in diagnosis and severity.
Anecdotally, I was an odd child and things got worse as I aged but eating disorders and severe anxiety were seen as discrete. I was diagnosed with an episode of psychosis which occurred out of the blue and has never been repeated when I burnt out and was hospitalised. I coped after a fashion and had DC. Maybe I was always autistic. I've never sought a diagnosis but am worried about my future ability to advocate for myself in healthcare settings as I also become selectively mute - I have experienced staff frustration and would like to avoid this in future.
Genetics played out - DS1 had worse anxiety, dyslexia, huge sensory issues, auditory processing issues and eventually diagnosed ASD. EHCP, tribunal, failed specialist provision, housebound for the last 7 years but he is settled into his routine now and I'm no longer on suicide watch 24 hours a day. I'm bloody glad he was never hospitalised.
DS2 was under SLCN from 2, eventually diagnosed ASD and ADHD. Never had the same anxiety issues. Home schooled throughout secondary but went to 6th form (maths, further maths and physics) and on course for uni. Already has an offer from local uni for engineering so can remain living at home.
So in their generation both diagnosed and one non-speaking as selectively mute and one non-verbal and speech delayed/difficult to understand requiring years of SALT. (Different to non-verbal and then acquiring 'normal' speech or remaining non-verbal.)
It is concerning that existing special schools are increasing provision and seeing an increase in severity. At the same time that mainstream schools are seeing an increase in severity due to DC not getting specialist places. I think absolute numbers have to be considered over time. Forget individual schools - how many places? If the number of places has increased then we need to consider why the number of eligible DC has increased in such a short time.