I know you can't supervise 'em in the air
. However you can ensure that they are authorised by an instructor or supervising pilot, along the lines of the military. This would encourage them to utilise the knowledge of the instructor and perhaps enhance the learning experience. It would be fitting as most people call the initally issued PPL a licence to learn anyway. I certainly leaned on others more experienced immediately post-PPL.
------------------
0 to 2000ft in 10 minutes