What courses can you take in high school to prepare you for a music degree?

If your school doesn't offer them, you may want to take some courses from a private instructor. My music degree is performance focused, but to prep for any music degree, music theory and piano would be my first suggestions, if you don't have a strong background in these already. Beyond that, harmony, and anything that falls into your area of interest- so anything that has to do with recording, mixing, overdubbing, etc. See if you can connect with recording studios in your area, there might be someone who is willing to mentor you. I'd recommend some business courses as well- they'll serve you well regardless.

If there aren't specific classes focusing on music engineering, you can always start a club/group with people who are interested in learning more. Or hook up with a local band or one at your school or talk to your orchestra conductor about setting up recording sessions during rehearsals. Any experience/initiative shown towards striving towards your passion will be seen in a positive light!

Alexis,
In addition to the great ideas shared by Jenny and Andrew, if you have an inclination towards music engineer, see if they have more technology-oriented classes this semester. Physics and mathematics would also help. Those will always add on to your skills as an engineer, while you develop your music skills through orchestra and your lessons. In future semesters you may find more music-oriented classes.
Claudia