Regarding Research in General:I have to admit that I was a little shocked to read the number 30%, even though my experience with homeschoolers has been that one (only one!) reason families choose to home school is that they don't feel a public school is giving them good special education services (and that is true for all kinds of special education issues, not just autism). I also know some families that have moved in order to be in a school district that is more friendly to special education needs.
Fortunately, most research on autism is not conducted via the school systems. Most research is conducted at medical and university centers with families recruited from the community. In my neuropsychology assessment experience, I would say that at least 30% of the ASD kids we see are home schooled, and many of these children are active participants in our research programs. (Emphases added. ASD=Autism Spectrum Disorder.)
All of this is worth paying attention to, as the vast majority of special education costs are not borne by local school districts (they get reimbursed), and obviously--in this economic climate--schools want to retain students.