If you've got a living situation like most high school and many college students, where you'll continue to have a roof over your head and food to eat even if you don't have a job, I've got some advice: quit your job.
That's a bit overstated. It should be, quit your job unless you love it. If you love your job--if you're doing whatever it is that is your passion in life--then stick with it. But if you've got some stupid job just to earn a little pocket money, quit your job.
Because here's the thing: Whatever is your passion in life is what you ought to be doing, and there's almost certainly a way to do it (or do important pieces of it) right now. That experience is going to be worth far more than a little pocket money. It will pay dividends for the rest of your life.
Some people--writers, artists, photographers--can just do whatever it is they want to do. If that's your path, though, take it seriously. Research both how to do your art and how to make a business of it. In fact, give that second part a special emphasis--start trying right now to make your art a business (if that's how you want to make your living in the future). Find out how other people make a living at it, find out how people get started in that field, and follow their example. By the time you get out of school, you'll have a good idea both whether or not you can make a living that way, and whether that's really how you want to make a living.
Other fields in the arts--music, acting--often require colleagues. Here your school may provide the best chance to work in your field, but there are other possibilities--musicians can play in bars, actors can perform in community theater.
In most fields, though, you can't just do the work on your own--you need a business or institution to provide some sort of support, whether it's equipment, colleagues with complimentary expertise, clients, government licenses, etc.
Sometimes there's only one path to a particular kind of job--you can't really become a surgeon except by going to medical school--but those are exceptions. Most kinds of work offer opportunities for a clever student who approaches them the right way.
Start by finding a firm that does the sort of work you're interested in, and then arranging to interview some people there. Tell them that you're working on an independent study at school. (Talk to a teacher at school and arrange to actually do an independent study, if you can--if you can reduce your work-load at school by a class or two, you'll have that much more time to do what you love.)
Tell the people you interview that you want to find out what it's like to work in their field. That's the truth, but it's not the whole truth: there are two other things you're doing at that interview.
First, you're looking for something that they need done that you can already do. Be sure to spot the easy, boring bits that anyone could do, but ideally, try to find something requiring some skill or talent that you already have, or that you almost have.
Second, make some contacts. Get names, phone numbers, and email addresses of everyone you meet.
Once you've had your interview, seen what they do, and made some contacts, you're in a position to try to get yourself inside. Based on what you saw, you may have a sense that they might hire you in some sort of part-time or intern position. If not, though, the next best is to volunteer.
Don't just call up and say you want to volunteer. They'll just direct you into their intern program, if they have one, or else tell you that they don't have any positions for volunteers. Call up and say that after the interview you've become very excited about the work they do there, and that you noticed one phase of the work that you thought you could already do, and say that you'd be willing to do that bit of the work for free if you could also spend some time watching how they do the other bits.
If the place doesn't have a rigid structure for how they handle interns, this ploy will very likely work. Once you're in, start learning how to do all the other things they do there, and start volunteering to do each of the new things you've learned how to do. With some luck--and some hard work--you may very well be able to make yourself indispensable, in which case you're in a position to ask them pay you. (As a minor tactic here, don't ask them to start paying you to do what you're already doing, even if they'd regret losing you. Instead, figure out what the next step up would be, and suggest that they hire you to do that job. Then if they turn you down, you're not in the position of going on doing what they just refused to pay you to do.)
It may seem stupid to work for free when you could be earning money. But there's nothing stupid about jumping in and doing now whatever it is you have a passion for. By the time you graduate, you could very well already be doing what your classmates have only been learning about.
Once you're out of school you'll be supporting yourself, perhaps a family, and very possibly a student loan company as well. In that situation, it's almost impossible to come up with the time you'll need to turn your passion into your livelihood. The time to do that is when you're a student--when the livelihood part is taken care of. If all you need to trade is your pocket money, it's very a good deal indeed.