Some depend entirely upon their families for support. A brother or sister or mom or dad are the only source of company. Friends are often absent altogether. It is easier to learn about the importance of relationships when their importance has been clear over a life-time. Insist that your child be included in regular classrooms.
Inclusion is a powerful way of building relationships.
And don't let anyone fool you into thinking that inclusion of children with disabilities in regular classrooms is a bad idea. Doing it poorly is a bad idea. Doing it well is good for all children. Remember that there are many people in the community who will benefit from knowing your child. Chances are your child has already made someone's life fuller.