|William Edward Cox|
There have been a number of Boston Grammar School students who have gone on to teach at their old school. One of those was William Edward Cox, who was a student 1921-1929, winning the Parry Gold Medal in his final year. He was a member of staff from 1950 to his retirement in 1971.
From the top of my head, others who have been both students and staff at Boston Grammar School include Michael Maltby and Steve Neal.