What are your son’s support needs, emotionally and academically? This will be the biggest determining factor of what to look for in a school/program. There are a lot of ASD programs out there; they can range anywhere from $3-$6k/ year and offer things like counseling, weekly check-ins and counseling sessions, academic coaching, EF coaching, etc. If he thinks this is more support than he needs, he may be ok with a school that offers very good support for all students. This is one of the reasons DD chose her school. They have a full ASD program, and although she didn’t feel she needed that level of support, she liked the idea of having a fallback in case she wasn’t adjusting well. She wanted a school that was very familiar with ASD and would advocate for her. They have a solid Academic Support Center and counseling offerings; they offer sevices to all students like sending an upper classman to class with a struggling freshman, then have the upper sit down and review the information with the freshman afterwards. She also chose to live in an engineering LLC (Living Learning Community) because the professors had offices on the first floor. There were classrooms downstairs as well, so she had some classes in her dorm. The TAs offered tutoring in the dorm Su-TH 6-10pm. This kind of gives you an idea of supports to look for, a school that tries to support the needs of all students is a good start. Here is a list of schools with a dedicated ASD program; it will give you a good starting point.
Let me know if I can answer any questions. 