We did similar in my previous school.
There was a separate ARB for children with complex needs and then the mainstream school had separate classes.
The ARB and mainstream classes rarely integrated (especially since covid), so each class would have the photos taken and then there would be a photo of everyone together.
The ARB would also have their own photos and a photo with mainstream and they were also given the choice of whether to buy the photo with the mainstream children in.
School photos are expensive and many parents will want to buy just the photo of their child’s class, rather than one with pupils from other classes in.
The parents aren’t wrong for wanting to do this.
I do not think the school is being ableist here, in fact I think they’ve tried to be inclusive but it’s backfired.
Of course if these children are usually part of the class then it’s disgusting behaviour but the article does hint at the children being in separate classes.