As a parent

I see two sides (at least) to this issue...
Yeah, I remember my mother and I going through all that stuff. I do in fact use the skills (writing, art) that she didn't think were useful, but not the way she or I were thinking of

.
As a parent and extremely ex-teenager, I realize that part of the attraction of arts is that you *know* what they do...you already play an instrument, and it's an area where you have more control over what you do than in your school work...so it's not too hard or unattractive to imagine being an adult playing that instrument...whereas in other fields, you may have only a hazy idea of what jobs are available, and if they involve deskwork, they sound suspiciously like SCHOOL. So, encourage your parents to understand that with new multimedia technology, music is not a dead-end - but also cut your parents some slack, and keep an open mind about all the career possibilities that have never occurred to you OR them.
I think your generation does have an added burden...most of your parents are probably my age (most of my friends' kids are teenagers now). We grew up in the shadow of the first wave of baby-boomers, and hunted our first jobs in the depressed '70s. We're not a risk-taking generation...we can see that the old system of good education + good, solid job is crumbling, but we're not confident about telling our kids to go ahead and take extra risks!
However, by the time most of you are getting jobs, the baby boomers will be retiring thick and fast...who's to say whether there will be more jobs...or fewer. There will certainly be big changes, so the only thing I am sure I want for my kids is that they should have practical skills and be ready to MAKE themselves a job, not just FIND one.
A freelance or self-employed person tends not to have a huge income (on average). On the other hand, you don't need to wait for an employer to give you a job...you normally own your own equipment and work directly with your clients. If you plan to be self-employed, learn about business and marketing - either at university, or from community courses. You can be sure that schools don't teach you anything that will give you more power in society, so make sure you learn those things for yourselves!
One thing I didn't realize when I did my degrees was how useful it can be to have a combination of skills...look at courses in other faculties, or even a double degree. You will probably find your interests broadening as you get older - now you are in a period of intense technical development, so when you think of your future, you think mostly of just playing your instrument flat out...but in 10 or 20 years, you could start to get bored! Other skills could give your musical career an extra fillip, or they could combine with music in unexpected ways in other careers.
Second, don't forget that performance musicians are...performing. Why wait till you finish university - if you're serious about music, you should be earning pocket money from your performance in your teens (I think so, anyway

). Can you move confidently and attractively in front of people, can you keep their eyes on you? Even as an orchestral, sound recording, or teaching musician, knowing more about posture, breathing/stress control, and choreography/movement can help - think about yoga, martial arts, Alexander technique, dance, mime, or drama. Nerve and small muscle injuries are often a problem, so anything you learn about prevention and therapy could help you or your future students...it could even be a career in itself.
Third, music is changing - and since it's a craft just as much as it's an art, you need to know the technology of your craft. I can't think of any reason (=excuse) for not knowing how to set up mikes for your own voice or instrument, how to record yourself, and how to either set up a portable sound system in a hall or outdoors, or use the basic sound system in any public hall. Practice in your school hall! It doesn't hurt to know how to edit music on a computer either...don't be a 19th century musician unless you plan to dress the part!
Now I have a kid of my own who looks about 50% headed for a music-related career

. You can be sure that I've been giving this topic considerable thought.

Sorry if I sound big-headed, I'm really just trying to keep this looong post as short as possible.