Jazz, as many other writers have pointed out, is increasingly taught in high schools and universities. It has become 'institutionalized.' This has had an obvious impact on the way the music is taught. Instructional guides are not new--you can find books on how to play and improvise jazz going back to at least the 1920s. But the amount of pedagogical material has exploded in the past 20+ years. A student today has a surprisingly large number of approaches or methods to choose from. None of the teachers I've had were dogmatic in their adherence to a particular methodology, but they did have preferences. In high school I was exposed to the Jamey Aebersold approach--basically a scale-chord method. You derive the melodic material you want to play from a scale or set of scales. There is more to it than this, and the Aebersold world is also closely connected to legendary jazz educator David N. Baker and his ideas on playing jazz. For all its limitations, and there are problems with such a heavy focus on scales (see David Ake's discussion in Jazz Cultures, U.C. Press, 2002), the Aebersold approach has introduced many, many musicians to the music. One of the central messages of all his instructional materials is that anyone can learn to play the music. With so much mystification around the process of improvisation, that remains an important lesson.
A few years ago, I attended the Stanford Jazz Workshop--a week-long, all-ages summer 'camp.' That program is structured around the ideas of bebop pianist Barry Harris. The 'Harris Method' is structured more explicitly around bop practice and focuses on creating smooth chromatic melodies through the use of certain 'rules' (for example, descending from the tonic, 3rd, 5th or 7th of a major scale add one half-step between the 6th and 5th degree). There is obviously much more to it, but the system is less about learning specific scales (e.g. lydian augmented) than about chromatically manipulating major and scales. Where things get interesting is in the harmonic underpinnings of this approach. For Harris the diminished scale has a foundational importance for the derivation of all the harmonic materials a player will use. Out of this focus on the diminished come a set of scales, what he calls sixth-diminished scales: a major (or minor) sixth chord combined with a 'related' diminished chord.
Although I attended Harris's workshops during my time at the camp, I wasn't sure how to incorporate his ideas into my playing. It seemed to involve a very different orientation to navigating the changes melodically as a soloist or harmonically as a 'comping instrument. It was only a few years later that I found myself returning to the Harris material. Frustrated with my 'comping--I felt like I was using the same set of voicings over and over again--I bought and started working through Alan Kingstone's The Barry Harris Harmonic Method for Guitar. That book, along with Roni Ben-Hur's Talk Jazz Guitar, have been immensely helpful, gradually changing some of my basic ideas and approaches to improvisation and 'comping. Both Kingstone and Ben-Hur are closely connected to Harris and explain the pianist's ideas in very clear and practical ways. Even more information is now available at Jazz School Online, a pay, e-school version of the Harris method (with video lessons by Kingstone and pianist Howard Rees).