I'm a bit surprised about this didactic method: being close to stalling on take-off doesn't seem to be a very safe way to teach a lesson.
I used to fly and during my license test we did get into a stalling exercise to force the plane to stall at a few thousand feet altitude. This was meant to learn the feeling of sudden drop and how to recover. There is something both thrilling and scary about transitioning so quickly from seeing the horizon to seeing only earth right in front of you approaching at a high rate of speed.
Being in near-stall conditions close to the ground seems to me like a recipe for disaster.