They may have had a private assessment, but you should still have a copy of the report. As mentioned above, symptoms must be present in more than one domain. I have (in the past) had questionnaires that were sent directly to form tutors, who filled them out without informing me. Send the FT an email to check.
If he has had a formal diagnosis, then he needs a code on the system remembering that ADHD is a disabilty.