The phrase "former pupil" refers to someone who used to be a student at a specific school or institution, but is not currently attending anymore. Full definition
I come from a family of teachers and was always impressed when for years my dad would be visited by former pupils thanking him for the opportunities he gave them. (legalweek.com)
The publication was impressive in its content and contained a list of former pupils who had been successful across a range of professions. (faith.org.uk)
Judging schools on how former pupils were performing at age 25 is to make schools responsible for decisions over which they have no control. (schoolsweek.co.uk)