Very true. If all the students are worthy of holding that rank then fine. All that I'm really trying to say is that I have seen a LOT of young black belts (in that 11-15 year old range) that couldn't defend themselves from a sack of potatoes...whether in "real-life" combat or in the sport version of martial arts.
And I mean the whole issue really comes down to your own personal standards of what constitutes a "deserving" person. People in general seem to think they deserve rewards just for showing up or trying moderately hard, but when I see a TRULY accomplished black belt demonstrating his skills I can't help but think that at this point I'd be ashamed to throw a black belt on.
Bottom line for me is, "if a 15 year old black belt can't defend himself against me (when I'm a yellow belt), then he needs to work a little more until he's worthy of that rank."
Aim first to understand; then to be understood.