British Graduation Songs

[writersaurusrex]

What song (if any) is traditionally played at graduations? (For example, in the US, it's Elgar's "Pomp and Circumstance March No. 1 in D", aka "Land of Hope and Glory".) Or do they play the school song, or does it vary wildly from school to school.

If it matters, it's for the equivalent of secondary school (specifically, Hogwarts).

Research: Googled British/English/Scottish (traditional) graduation songs, British/English/Scottish graduation traditions