There has been a lot of good advice on this topic Donald, so please use the knowledge that you have been given wisely. With that said, here are my $.38 cents worth.
So you finish high school and are left saying, "Now what?" Do you just up and go somewhere and start busking in hopes that you may land some ongoing gig somewhere? How much material do you really have? How many performances do you have under your belt that would showcase both your talents and professionalism? Being in high school, my best bet would be that you don't have much experience for any of the questions I asked. So then what do you do? Donald, nobody here is saying that you HAVE to go to college as SOON as you graduate high school. Hell, most take a year off before starting in the second half of their lives.
This time off can help you really focus on you and your magic. Book as many shows as you can. If you do not have business cards, get some. If you do not have a demo reel, get one. Write a press release about yourself and put it in the newspaper. It's free, and will help get your name out there. However, if you do not feel that the material you have is strong enough to book shows, then maybe you need to take that time to work on your act. Refine it, work on it some more and refine it again. Draven seems like a real worker and I am sure he can offer some sound advice when it comes to performing and booking gigs. And I am sure he can tell you that his work is not always steady. Hell, I went from working full time as a bar magician working 4 nights a week, 2 shows a night, to only working 2 nights a week, 1 show a night. And now I have a part time job to suppliment that lost income. But I also have provided to me free medical and dental form the Marine Corps, so I can AFFORD a part time job.
Just because you go to school does not mean you have to give up that dream to becoming a full time magician. Hell, do you realize the opportunities that are available to you at a university? You will have unlimited places to perform at, and really work on your performance skills as well as your socialization skills, all while furthering your education. I worked with nothing but a college crowd for quite some time, and I can tell you this much. They are a tough crowd. Which is a GOOD thing, because you are gaining the knowledge on how to work a tough crowd early on. This will help you in the long run with audience management. You need to realize that for what you/we do as magicians, we can perform anywhere if we so choose to. I only wish I had attended a university at a young age. So with that said, look at what magic is all about, and as Draven said, think about business management or marketing or hell, even psychology as the way to further your education.
Some people make it in life without a college education...(Richard Branson of Virgin music is one that really comes to mind. He dropped out at the age of 16, and is now a mega-millionare.) Some people do NOT make it in life WITH a college education. Life is what YOU make it. If you want to be a professional magician, so be it. Just know this:
You can jump out of a second story building with or without a cushion to land on. I would like to know that I have something to fall on if I do in fact jump...
Mike