I've heard as many different opinions about Education/Accreditation as there are models of harmonica! Now, for my two cents....
My personal take on all of this is that ALL education (whether barroom or theory class) is valid. I mean, I count learning theory right up there with chatting with Sonny Terry when I was just starting out or having "Earring" George Mayweather show me the intro to "Early In The Morning" a la Junior Wells.....I was "schooled" to play blues harp in the bars, streets, ect....however, at this time in my learning process, it's only natural that I want to learn MORE...Interestingly, I'll be attending UMASS here in Boston in the fall and will be majoring in music...now, it would help a great deal if the music department taught my instrument, but they don't....now, I'm faced with not being able to study the Chromatic harmonica exclusively because people JUST DON'T TAKE IT SERIOUSLY like they do piano, guitar, oboe, violin, ect. I'm pleased to report that UMASS is currently looking for someone who can teach me MY instrument so I'll not be forced to take something else and apply my knowledge to the Chromatic on my own time....the arguement for education is not to "grade" harp players, but, to help them learn as much about their instrument as they want to.....believe me, as a self-taught musician I agree that no one can teach "soul" or grade talent, but I also know that without theory and all that other scary stuff (for most self-taughts) I'll never be able to play ALL music...Unless of course I happen to learn to channel Charlie Parker!