Mrs B & I did that for several years as instructors with the National Motorcycle Training Scheme (Star Rider). The local schemes ran on school carparks on Saturdays.
The local dealers delivered new bikes & riders to site at 9am & we could usually get them safe enough to depart without supervison by 1pm, though those who had not made enough progress to be safe phoned the dealer, who took the bike away & brought it back the next weekend. This was the Star Rider Bronze course. The scheme was run in such a way that the scooter rider scenario described would just not have happened - I don't recall ever having a bike damaged on a Bronze course, though several riders came back for more than one session.
The Silver course took them up to test standard - 6 x 4 hour sessions on road, with a maximum of 4 riders per instructor. This was Star Rider Silver.
There was also an advanced course (Star Rider Gold), based on Motorcycle Roadcraft - 4 x 2 hour evening theory sessions, 8 x 4 hour on road sessions then a 2 hour on road assessed ride by an independant examiner. We completed & passed the Gold exam, but Star Rider imploded before we could do the Gold instructors course. The Gold instructors course was reckoned to be as high a qualification as you could get at the time without being Police.
The Part 1 test came in while we were instructing & we spent a couple of weekends acting as "dummy" candidates for the trainee examiners - quite fun putting in faults at the instructors request to try & catch out the trainees, though it was usually the times we were asked to do a "clean" run that flumoxed them. The test course was laid out with cones in the school playground. At the time, there was much made in the motorcycle press about the "impossibilty" of completing the test on certain bikes of the day (RD250LC comes to mind) - several of the instructors proved that this was not the case, it was just a matter of technique & control.