Hi OP, you should post on the special needs:children board. There is more traffic here.
Has your DS been giving a diagnosis, how old is he? (Just being nosey).
But to answer your question, DS who has ASD and verbal dyspraxia, would hopefully be going to a speech and language school. Some children with autism can be very sociable, equally some children who only have language disorders as such can be very unsociable. It entirely depends on the child, my DS is sociable.
Some children who are usually admitted to SLCN will have social interaction difficulties, regardless of diagnosis. On the other hand, some children are more engaged with children, with similar difficulties to them and hence they become more sociable.
I think if you are worried about the social aspect, I'll advise you start placing your DS into outside clubs/activities, if you want to widen his friendship group. DS goes to his football class every two weeks and he has made two good friends there.
You are doing the right thing by placing your DS into a specialist school.