Not too long ago, I was trying to cheer up a friend about a professional set back he'd experienced. I jokingly suggested he take an "external validation" class--and then realized my Freudian slip; I'd meant to say Education class. But I wasn't really wrong. I've noticed marked differences in the way the class is run and how performance is evaluated in both my Ed. and Science classes, and it's very interesting.
The Ed. class tends to be more nurturing: we discuss and respond a lot and, when mistakes are pointed out, it's usually as part of a larger, positive comment. The Science class is a refreshing change from those back in the dark ages of lecture, lecture, lecture (now it's lots of doing, not much sitting), but there is regular assessment and you know exactly where you stand point-wise (i.e. exams, quizzes, assignments). So it can be externally validating, if you are doing well, but not so much if you forgot to do the reading.
The education class is an advanced class, so naturally there is more synthesis and discussion going on than the Intro class. But I think both approaches have their benefits; however, like everything (say, yoga snark, for example), it takes a light hand. I think it's important for students to feel safe to be wrong; I think it's important that students--eventually--get their information correct. I think different viewpoints are a crucial part of seeing the big picture; I think that some people confuse opinion with fact, or want their opinion to be considered fact, despite proof to the contrary.
Both approaches work for me. It seems like they should be contradictory, but I find the combination kind of soothing. I can enjoy the energy of debate (albeit very gentle and supportive) in one; I enjoy feeling like I'm laying groundwork in the other. I don't mind loosey-goosey part of the time, but the Type A/Big Sister/Striver in me likes to have a number in hand.
And, as we continue to talk about how to train yoga teachers, I see the need for both in a YTT syllabus (obviously, we don't need a lot of facts and hard assessment in a regular yoga class for practitioners). You have to understand (maybe there is a better word) yoga from both a personal and a physical perspective. These are the metaphysical benefits and this is the muscle that needs to be open for a Down Dog to happen. This is the way you might feel during pranayama and this is a Sanskrit name for Extended Triangle. One type of information is easy to present, one isn't.
With a really well-crafted YTT program, both would happen at the same time. As with any good class, a teacher can encourage and allow students room to experiment, but also correct mistakes and get the misdirected back on the right path. You should have a good feeling about what (how) you are learning, but you need structure. How to insure that? Probably a system of assessment that includes both written elements and observation by peer teachers. A guarantee that the teacher trainers have been trained to teach (for public school education, you are trained by education professors, not your colleagues). A set of standards that should be met--altho they can always be expanded on.
And, I suppose, if you're really paying attention to your yoga practice, you can eventually dispense with the need for external validation, all together. But for most of us mere mortals, that's an assignment we're still working on...