ignominious you must be a kindred spirit!
How did I learn jazz? I went back to piano when I was sahming dd, tried out some easyish classical pieces (Einaudi
etc) but they bored me. So I thought I'd give jazz a go instead, and completely by chance found a teacher of jazz! It was a lucky find.
I've always had a good ear, but I was a poor sight reader (or so I thought..) and my technique was a bit lacking too.(Still is...)
I started off doing random stuff from the syllabus (abrsm) but didn't want to do grades as I go to pieces in front of people. But suddenly I thought "why not?" and decided to go for grade 8. I don't have any other grades but my proficiency level and theoretical knowledge in terms of classical had stagnated at about grade 6. It was hard work, but I got through somehow.
I agree with you about the abrsm pieces. They don't offer enough opportunity for improvisation, imo. If you, or your pupils, need a jazzy challenge I'd recommend Lcm or even Rockschool.
The Grade 8 is not terrifying! There is a piece (I did Taste of Honey), from the book and two improvised pieces (I did Misty and Lullaby of Birdland) which you take from a Real Book and interpret. There's an aural test, musical awareness, creative response and the dreaded scales.
In my experience there is a lack of coherent support for theory. I enjoy the theoretical side of jazz particularly and I've put myself in for the grade 8 Popular Music Theory exam. Now that IS terrifying.
Sorry that's a really long post. Typical self-absorbed jazzer! If you want to know more, feel free to pm me.