Moody:
Does master mean the teacher or a pupil since in regency times boys were called (young) master ...
In that case it meant teacher, but boys were also addressed as 'Master', a sort of diminutive of 'Mister', and that was still common when I was a boy in the 60's, particularly when addressing an envelope. It was most unfortunate for any boy whose surname happened to be 'Bates' !