Here's an experience of mine that relates to my personal best impression of Jaco's genius and work ethic, and schooling in one form or another:
Some here probably know of Scott Henderson, a brilliant guitarist.
Before he achieved his present recognition, he was a local player in Los Angeles, working his way up, starting with Jean-Luc Ponty and then on.
But before this, he was a grunt like many of us are/were. SO, we went to see him (he was a buddy of a friend of mine) playing at a local bar. Cover Band, Him, Drums, Bass, Female Singer, all except Scott-Totally average bar band players, nothing there.
They were finishing up a version of "Cocaine" then took a break. We went over to see Scott- The rest of the "Band" (he was a hired-gun sideman of course) was drinking, yammering, having fun at the bar. Cool.
Scott was sitting at a table, by himself, with an excercise book open, and he was on his own, doing practice transcriptions, harmonics, modes, etc. By himself, for himself. Up until it was time to play their BS for the next set, which I might add-
Scott played great stuff on their standard repertoire of Classic Rock, Blues and such.
A real Pro, capital P.
I have no idea of Scott's musical education or background, pretty sure he had some formal schooling, makes no diff.
The best passage I remember reading about Jaco was how on the Tour Bus for the CC Riders, the others were playing cards and making jokes, Jaco was plugged into earphones woodshedding and running modes,
When I was beginning, I practiced thru the night til my fingers almost bled! (Drama!) Not so much now, but I still do a work-out daily.
I was fortunate to have studies also with the Great and amazing Dave Parlato ( from Barbara Streisand to Zappa!)
and HE had studies with a gentlemen whose name he told me but I forget- who was one of the Principle Bassists with the LA Phil, and that ain't chickenfeed!
Learning is a process, school or the bandstand, or at home. I shudder to think of where Jaco might have gone had he lived longer in better mental health.
Beat to death by a Bouncer...One of Music's tragic notes in History. Takes a Bass Player to get that.
I remember hearing "Donna Lee" and thinking to myself...
"RUH-ROH!!!"