jdinca
Master Black Belt
I'm going to agree and disagree - students can fail; if they can't, it's not a test - it's a demonstration. However, whether or not a student tests is up to me - if I haven't cleared the student to test, and s/he shows up thing s/he'll test, s/he'll have quite a shock. I have had students fail, usually due to nerves, although I have had the occasional student who thinks s/he's hot stuff blow off testing (walk through techniques, not try, etc.) and fail that way - but it's fairly rare, because I won't let a student test if s/he can't pass - that's poor instruction - but neither is passing at testing guaranteed.
We always do a pretesting to determine who is ready to test - and my assistant instructor and I decide together who is and is not ready to test, and then the students are informed of our decision. If you're not ready, you don't test - and I've never had problems with it; in fact, when I've told students they aren't testing, the usual response is "thank you - I didn't think so either" - including one girl who was 13 at the time, who told me that she knew she wasn't ready, and if I had told her to test, was going to ask if she could wait for the next testing, because she didn't want to get up, do badly, and embarrass herself or the class.
There's actually no disagreement here. I've never had a student go through a test without my approval, but it has happened on occasion. Typically, it's a young student with parents pushing from behind, or a student who's become somewhat "teacher deaf". It is on the rare side, though. I've also turned down a few students who wanted to test. Some students have been tested who didn't think they were ready just because I knew they were and wanted to give them a confidence boost. Trust me, I wouldn't do it if I hadn't mentally already passed them. These are usually tests done in a private lesson, as opposed to going before the belt board. If a student is moving well enough during the belt prep, I'll make it a test and the student doesn't know it until I say "congratulations".
These scenarios, for the most part, are all in the early belts. When a student gets to the point where they're ready to test for, say, advanced purple, or blue belt, things get much more structured. By this point, they should have a decent understanding of how the system works and what's expected.