A most interesting discussion regarding spinning, etc etc.
I have been spinning on a regular basis for thirty odd years,
(cessna150/152, sometimes 172) and always commence at 4,000AGL, recover by 3,000.
I would NEVER allow a student to use anything lower, as for an instructor doing a max rate turn at 600ft, he must be an accident waiting to happen, not to mention setting a very bad example for his student.
I recently was training a commercial student, and in a max rate turn he lost it, and we spun(172). I did not touch the controls as I wanted to see what he did, which was to lose over 1,000 feet!
Quite an exciting ride.
I believe as instructors we have to set an example, which is why I insist using 3,000ft AGL for all steep/max rate exercises, and higher for spinning.