Interesting that you are saying that students may practice stalling when solo.
As a PPL with about 100 hours, I pre-flighted a club 150 one day and couldn't get a peep out of the stall warner, so when at a safe height, I tried a deliberate stall; still nothing.
When I landed, I recorded the stall warner problem in the tech log. A couple of weeks later, this aircraft spun in with 2 fatalities due to CO leakage.
The club owner asked to see me next time I flew. When I explained about the stall warner (according to the tech log, nothing had been done to fix it when the aircraft crashed) he went spare ranting that I shouldn't do a deliberate stall unless I had an instructor on board!!