diagnosing aspergers what should happen?

My son (9) was referred by the school doctor for an asd diagnosis.  He was recently seen by a community mental health paedeatrician who took him into a room for about 1 and a half hours.  At the end we took him home.  2 days later we received a letter from the school doctor stating that the mental health team concluded he did not have asd.  I just wanted to know if that is what usually happens as we were not spoken to/ask questions at any time by them apart from completing an AQ Test.  This was also the case for the school.  I am from Scotland and wondered if this is how assessments usually happen.