What are exams for?

Daft question?  You may think so - surely exams are a way of testing how much a student knows about a subject?  Well, they may have originally been designed with that objective, but things have changed over the years.  Today it seems to me that exams are trying to do two things - and two things which are fundamentally incompatible.  From the point of view of the government and schools, exam results are a way of assessing how well a school is performing. So both government and schools want to see as many A and A*s as possible. But exam results are also used by employers and further education establishments to try and identify candidates worthy of consideration for a job or a University or College place.  And they want results which clearly separate the wheat from the chaff - if everybody is coming to them with A and A*s how are they to differentiate?  So I come back to the original question - what are exams for?  We need to make up our minds.