Looking4hope is correct. You can keep your child in private school and request an evaluation under the Child Find provisions of IDEA. Under these circumstances, the quality and attention paid to the evaluation is highly variable but it does have the effect (in many cases) of letting the public school know that your child may be enrolling soon. If they believe that, the evaluation is apt to be more thorough.
in my opinion adolescents need the legal protection that being a public school student with an IEP affords. There is NO group of kids for whom this is more applicable than "ours." In some cases, public schools will opt to send a student to a private facility, which is fine if it is appropriate. The way to get the public school to shoulder its responsibility for your child is to ENROLL him. Otherwise, the longer you pay privately for whatever your child needs, the happier the SD is.
Martie