Hi there, I worked with autistic children. The course may provide your Sister with help in dealing with him. The main symptoms are a lack of attention, hands in ears, climbing, hyperactivity, sensitivity, paranoia.
The main ethos of the school was physical activity and I highly recommend you keep your Nephew physically stimulated, this produces endorfenes which then help with menatl concentration. An activity which was particularly proven to assist was roller blading - the children had to concentrate and it stimulated there need for physical endurance.
You need to discuss the condition with a Medical Profession/Social Worker, there are rest bite centres and schools provided for autistic children.
I hope this helps a little bit,xxx