Have they looked at anything other than ASD though thrifty? Non Verbal Learning Disorder, Social Communication Disorder, etc?
As Bochead suggested, could you go back to your GP for a referral to someone more experienced in complex cases and teenage presentation?
It sounds to me as if he needs a full multi-disciplinary assessment, rather than just the opinion of one psych. The mutli-discip team here comprises lots of different professionals and the assessment process is centred on the child, rather than a standard format.
The assessment often involves a few weeks of school observations and home visits by various professionals, then either a full day or half day at the assessment centre, depending on the results of the information gathering process.
This is from their leaflet:
^"THE OVER 6 TEAM is a multidisciplinary assessment team of health
and education professionals. We will create a unique ?team? based
on your child?s individual needs.^
^The team may include: a paediatrician, psychiatrist, specialist health
visitor, speech and language therapist, occupational therapist, clinical
psychologist, psychotherapist, family co‐ordinator, specialist teacher and
or an inclusion support practitioner."^
Ds had everyone except the family-co-ordinator and SALT involved in his assessment and SALT was done retrospectively, as it was an oversight on their part.
If your GP can't refer you to something similar in your area, you can push for a GOSH referral, but the problem with that is that you need CAMHS agreement for the referral before they will accept you. Referral info here. I think you can pay for a private referral, but you need to contact them directly for more details.