Of course, it is always possible that your local community has a special private offering, such as a co-op school or alternative learning center, which is appropriate for your child. And it is certainly possible that your child with autism will develop the skills needed to attend a small private high school. But all of the pieces need to be in place for typical private school to be a viable option.
"Special" Private Schools and AutismThe Philadelphia area (where I live) boasts more than a dozen special needs private schools. Of these, only a very few are very likely to accept a child with autism. All of these accept ONLY children with autism. The others may consider an autistic child -- but will accept such children only under unusual circumstances.
The reason for this is fairly simple: most special needs private schools are designed for children with typical social skills and poor reading skills. Autistic children tend to have problemmatic social skills and good to excellent reading skills! In addition, autistic children have the reputation of being more difficult to teach than learning disabled children -- a reputation that may or may not be deserved!
Those schools that are specifically set up for autistic children have the great advantage that everyone on staff knows and understands autism. They may also have a wide range of therapeutic resources available on site, all of them potentially appropriate for your child.
On the other hand, of course, these schools accept only autistic children, which means that 100% of the children your child meets will be...autistic. This means no typical role models, no typical activities, and no typical community involvement. In addition, the cost of "autism schools" can be astronomical: as high as $50,000 per year or more. While it is possible to convince a school district to underwrite an approved private school placement, it is usually a tough sell -- since such schools are actually the MOST restrictive environment available.
Schools for autistic children are usually a good match if your child is either profoundly autistic -- and thus unlikely to do well in a less restrictive setting -- or profoundly unhappy in a typical setting. In fact, some children with Asperger Syndrome may do better in a school for autistic children, since they are often extremely sensitive to the inevitable teasing that goes along with inclusive or mainstream settings.