How and by whom? I've been an instructor for twenty years now and spin training was already deleted from the syllabus when I got my own license. My instructor training didn't include spinning either. None of our training aircraft (mostly Pipers) is cleared for spinning. So we would have to send our students to some aerobatics instructor who does the training on his Pitts or Extra. Totally different aeroplanes from what they are going to fly with their PPL. Different spinning behavior, different recovery technique. We rather teach stall avoidance and proper speed control instead.
Interesting point, so what happens if a student does something daft during stalling like trying to pick up a dropped wing and puts the aircraft into a spin for which the instructor has never been trained to recover?
You can teach speed control all well and good but when something goes wrong it would be very easy for a low hours PPL to get distract and find themselves slow....pretty sure there have been several GA incidents over the years where the final moments have been an entry into a spin at low alt...
As for who / what, well I trained on C152's with mostly Mil / Ex Mil instructors who were more than comfortable with spinning, certainly no need for an Extra or a Pitts.
Just my thoughts anyway, as I said its no doubt been done to death already and I can certainly see both the pros and cons for it.... I am however glad to have had the training though never had cause to use it other than intentionally...