Ultimately he has to find his own path. It may or may not involve being a pro musician.
I can empathize with the feeling that the school is not teaching him what he wants. But too some extent I doubt he knows what he actually needs. If he wants to be a pro musician I think he will be a lot more successful and have more options to change life paths if he gets a formal education/degree. However, I do think society currently seems to hold degrees in very low esteem, and I would be concerned with him racking up a lot of student debt.
My path was in and out of music. I started on viola in 5th grade, crossed to upright around 8th grade, dropped out of music as HS junior to take vocational electronics, and joined a university big band as a HS senior. I never dreamed I would be a full-time pro musician, but somehow I found "my" path.
I originally wanted to be an engineer similar to Agehorse and tried going through the math track at my local junior college. Unfortunately, while I could do the math I feel I have some memory deficits that made progress increasingly challenging.
I was also taking the music courses I thought were important, ear training and theory. The college had shut down the jazz/commercial track the semester I started; so the only option for me was the classical track. On the positive side, tuition was dirt cheap.
For third semester I gave up on math and declared a music major, which meant taking a lot more music classes. I also brushed up on upright and auditioned well enough to get a half scholarship. Many of the required classes were not subjects I was particularly interested in, but I was surrounded by a bunch of peers who were very positive and excited to learn about all things music, and their excitement was contagious.
Somewhere along the way I bought a Real Book and started learning how to read and interpret chord notation. I drew on what I had learned in classical theory and one of the guitar instructors provided mentorship once or twice a week.
I dropped out after third semester, got married, and joined the military as an electronics tech. I enjoyed the job and was good at it, but I really missed music. I continued improving my skills reading chord notation and playing along with recordings. My first assignment was to Turkey. I volunteered to play in a backup band for the base talent show, and that led to the formation of a cover band.
There was a professional military band at my second assignment. I continued reading the Real Book and bought a really crappy Kay upright and started playing through Simandl. Eventually I won an audition and cross trained into the band program. I'll be honest, I was not qualified as most of my peers had BS or MS degrees. Some even had completed their doctorate. But the careerfield had multiple vacancies; so essentially they were desperate enough to offer me a job
.
I worked really hard to develop the necessary skill and had a long and successful career. The job was pretty ideal for my particular interest and skillset. In fact, I doubt there is any other musical path I could have taken to achieve the level of success I had. So I feel very lucky.
Something that I think is really important is a lot of musicians become disillusioned with the job. I knew many fine players who put down their horns and decided to follow a different path. Many of them had a large amount of student debt. However, I think having a degree was an advantage for them.