Triggered an old memory I hadn't thought of for a long time. So....I first trained in Greek Goju Ryu. It was my first art and I loved it. But the guys who got me started in it stopped going as frequently, and I couldn't get there as much as I wanted to. (almost two hours public transportation) Left after a few months. Man, I was big time bummed.
Shortly afterwards I found a school in a nearby town to me and started going there. A couple years goes by, I'm a green belt now, and the fellas who started me at the other place stopped up to see me. I was working out with another guy and these fellas watched and commented to each other "brown belt technique, brown belt technique, black belt technique" (they were kind of shocked that a green belt would be doing something that they themselves had yet to learn)
They stopped by a week later with their gis and we did some friendly sparring. They were both brown belts. Remembering their comments, I only threw stuff they were not familiar with. It was like shooting fish in a barrel. That always stuck with me.
It's why I give the students a lot to choose from. If a student asks me "Can you show me how to throw a jump spinning back kick? I'll say sure, but first you have to learn a back kick and I'll teach him that, then you have to learn to take to the air and teach him that. And let me show you what can happen when you do that - and I'll throw one and have one of the black belts just rip me out of the air and crash me to the ground like a shot bird.
Just like there's some students who will never be athletic enough to throw that kick. No matter how long they train. But they'll learn how to counter or neutralize it. And they love that. Obviously that has nothing to do with self defense....except for a little bit. Teaches you to play the cards you're dealt, how to overcome certain physical things, teaches body movement, distance, timing etc etc.
And we never actually had a curriculum necessary for the advanced of rank. Sometimes white to yellow, but that was about it.