You missed a golden opportunity to say "See? that's what happens when you go out without your instructor."
I have been known to ride along leaning in through the passenger window and chatting to the driver "excuse me love, I wonder if you've considered getting driving lessons and going to a proper driving school with decent instructors?" The instructor, sitting between us, was going a funny colour as he knew they were in the wrong so couldn't say anything in defence.
On another occasion the instructor did prevent the pupil completing the overtake too early and squashing me (on the first three attempts) by pointing at the mirror, but when they finally cut me off and slowed down I overtook and cut them up (cue horn sounding). I don't think they were happy that I took a short cut then and so was sitting at the side of the road waiting for them
The instructor looked embarrassed and I nodded knowingly when he caught my eye. At the next junction they wouldn't wind the window down for a chat. But they did at least change lane afterwards to overtake me, which got a very pointed thumbs up.