Hi Dudes!
I've followed the ABRSM Jazz Grades syllabus on Trumpet, Alto Sax and Trombone, and done the exams up to Grade 5 on the first 2. I found them an excellent structure of learning, the tunes are all pretty authentic and give a wide range of styles to cover. Improvisation is part of the learning - from 8 bars in Grade 1 to 32 bars in Grade 5, and tunes, which can be performed with CD backing or live musicians/band, are usually about 2 minutes or so long, involving either 1 or 2 choruses. Scales etc include modes, pentatonic and blues scales, and can provide an excellent structure for learning, and the exam takes into account that some people are better at sight reading and some are better at playing "by ear". Various theories abound about why there are only 5 Grades:
1. They are at a slightly higher level than classical grades.
2. There is not enough interest beyond Grade 5.
3. It cost a lot of money to set up - cannot be repeated.
4. It was an expensive experiment.
and perhaps others.
Trinity Guildhall do jazz grades for sax up to Grade 8 but not for trumpet/trombone. Thames Valley University (TVU) administer the London College of Music Jazz Grades, which cover sax, trumpet & trombone up to Grade 8, and are pretty good but I would have preferred The ABRSM system. Following the syllabus does not necessitate doing the exams but is a good structure nevertheless (I did up to Grade 5 on Trombone but did not submit to the exam process in that instance).
So, highly recommended, and would allow you to structure your learning and assess your ability at the very least.
Kind regards
Tom