Inclusion is a babrbed gift.
Many, probably most kids with SN thrive in MS with the right support (that's a prime caveat: many children never see anything like that). however there are some who will never cope with an inclusion environment and it is right that they shlould not be forced into MS.
Autistic often but certainly not always fall into that and Retts isn;t autism but oioften is associated with it (usually IIRC).
There are also degrees of inclusion: ds3, and hopefully ds1 at comp level, attends a unit which is within a MS school but is separate and the children receive 1-1 to access MS when appropriate. DS3's is an all- SN unit; I hope ds1 will get a place in one for AS.
The keys are the actual child and the resources in place. If a child with a sensory or asd type disorder collapses to the ground covering tehir ears every time a child laughs becuase they can't handle thenoise, or switches off becuase of the sheer bustle of a normal classroom (DS3 was the latter ) tehn an MS calss will only be damaging in the long term. Likewise a child such as my ds1 who responds to noise etc as a perceived threat and lashes out. Why should he ahve to suffer the consequences of that, or the others in his environment be aplced at risk?
OTOH mys chool was one of the earliest ones to rpactice inclusion adn I feel I benefitted hugely from a very happy young man being included in my class. he had CP at a similar level to Riven's DD and a 1-1. Obviosuly I cannot entirely trust my perception of the situation as I was but ten, however it seemed to work: most kids, regardless of ability, thrive on the company of their peers.
The other aspect is provision; well resourced inclusion is one thing,, many LEA's have polciies such as no more than 16 hours a week in MS with a 1-1: it ws such a policy that IMO harmed my ds3 (here as in many palces you have to fail in MS to get into a SNU provision).
So what it coems down to is there HAS to be a mix of provisions. It's all very well saying we need all children with SN to attend MS for erquality but that wpuld mean sacrificing some children to the lions- bullying, non differentiated expert teaching, sensory overlaod, access issues etc...
My speciality is Autism so I naturally focus on that but I believe specialist autistic units are wonderful provisions, as are general SN placements. And as is inclusion. WHEN used properly and with regard to child before budget.
Now, I would love to see far more good quality provision of the type ds3 attends, where MS children and SNU chidlren receive apporpriate schooling but get chances to mingle. Even then soem very severely affected children are not able for that and that has to be respected. Equality is a great thing but should not be put above the needs of the actual child- eqiality of life quality is as important as eqiuality of anything else.