I just read these posts again, and all make valid points. The one point that I don't see, is, as a potential student, (or attendee)..........
.....that student should decide ahead of time, exactly what knowledge or skills they want to learn. THEN, decide who's training regimen fits their objectives. Most instruction follows a syllabus that may not be as flexible as the student needs it to be.
Communicate with a potential instructor, and make sure the goals of both parties will be met........
