My tutor at university understood this very well. In my first week he told my tutor group "At school you were all the best, now it is likely that half of you are below average".

Another thing I noticed at university was "improvers syndrome". When I took up some new sport or hobby, I always thought I wasn't progressing very well, because I was comparing myself to the people around me who were all improving too. It was only at the start of a new year when lots of newbies arrived that I realised how much I had progressed.