I would say to someone that wants to quit school from music, that a degree in something that could mix well with music.

Electronics : work with amps, guitar wiring,...
Computers : program music softwares, mixing music
Administration : start a music store, be part of a music industry as a worker, build your influence network in music while getting a regular paycheck..

There's so many possibilities to be working in the music business.

Take Piet Sielck as an exemple. (People who listen to powermetal will know him). The guy is a sound engineer, throught the years he manage to work with really great bands. Then decided to form a band of is own (Iron Savior). You know what, he now have a few albums under his belt but works with people like Kai Hansen (Helloween, Gamma Ray), Dan Zimmermann (Freedom Call). He had a good job and got to have a good influence network that helped him to have a job and a band of his own. If the band would not have worked, he still had his day job.

Well I guess this is just my two cents