Hi @SilentStorm7 - the first suggestion I have is to read the essay sticked at the top of this forum titled “Double Degree Dilemma essay (written by David Lane).” It will give you more information about the different ways to study music in college.
If you want to be a K-12 band director in a public school, then you would want to look at BM (bachelor of music) degree programs with a Music Education major. They will be found at schools of music within a college or university or at a conservatory. Most BM programs require an audition, though often the standards are not quite as high as for performance majors (depends on the school and on the instrument). A Music Ed degree program will generally give you a solid background in music theory and will teach you to play a variety of instruments and how to teach students to play them. It also includes coursework in conducting, piano skills, instruction on your primary instrument, ensemble work, as well as education coursework and student teaching required by that state for teacher certification. You would graduate with teacher credentials that allow you to teach in that state. Some programs, especially those with a national profile, also have reciprocation agreements with other states to facilitate teacher certification.
Many public universities have good programs as well as connections in the states where they are located, so if you want to teach in a specific state or region, it often makes sense to get your degree in that state.
To start, I would look at Music Education degree opportunities at the public universities in your home state, since they are usually the least expensive options. Ask all the band directors you know locally where the good music ed programs are, and where new hires and student teachers generally come from. Look at the professors on your primary instrument at those schools and see if the studio is well regarded. See if the school has a marching band, since that would be desirable for band directors as well as those interested in Drum and Bugle Corps. Have recent grads from your school band gone to those schools? Even if they are not majoring in music they may still be in marching band, and will likely know music majors at the school.
Beyond your home state, there are Music Ed programs that have strong national reputations, as well, and if you are a very strong player on your primary instrument they may offer you a stronger peer group and instruction from top professors. Ithaca College, Northwestern, Michigan…many of the best music schools also are strong in Music Ed. re: the UCs, if you are not a CA resident, California public schools do not give need based financial aid to out of state students, so unless you can afford to pay full out of state price, they will be a very expensive option. I am not sure what music merit might be available in California schools as I am unfamiliar with west coast music programs.
Are you a junior right now? Look for leadership opportunities in your school band - drum major, section leader, etc. cultivate your relationship with your band director, as he/she probably will be writing you a recommendation. If you do not have a private teacher on your primary instrument, you should start taking private lessons and make your teacher aware that you are planning to study Music Ed in college. Your teacher likely will have suggestions that will suit your goals and your current level of musicianship. If you are a junior, you also will need to get started on audition preparation if you have not already begun, and your teacher will help you with that. Private teachers frequently write recommendations, as well. Most of the schools my son has applied to required 2 music-related recommendations, one required three. Consider doing something music related this summer - a camp or festival that focuses on your instrument, volunteer at a local band camp for younger kids, teach some private lessons to younger kids, that sort of thing. Try to get your college list nailed down the summer before senior year, because you will need to be mindful of deadlines and audition requirements and plan for them. Write most or all of your essays during the summer. Applying to music schools is a more complicated process than general college admissions, and the deadlines are earlier (often by Dec. 1st). If you are doing marching band, it will be VERY tough to manage your time fall of senior year. We just went through that and it was VERY hard. One of my son’s friends didn’t keep an eye on deadlines and lost the opportunity to apply to several music schools she was interested in. She was looking at Naviance at general school application deadlines and didn’t realize the music school deadline was a month earlier.
I hope that helps! I’m sure others will have more to add.