yep,
instructors that teach kids to go out and operate close to the ground in their working life - I think that's nearly everyone - well if they don't teach them how to stay away from the ground - well they want their backsides kicked until their nose bleeds.
Especially where it relates to the "subtle hazards of light winds" which Sasless has remarked upon.
Like i say, if you really stuff it up, and pick up you own dirty air for a bit of freefall VRS, you'll usually only ever go about eighty feet before the pucka factor saves you, but if you start at fifty feet - well it's really only the last thirty that will hurt eh!
if you don't get a reaction from a student on that one I suggest going back for the coffee - again - and another student.