If there is a law school near you, often they have "open houses" a few times a year. You are on the young side but there is no reason you couldn't attend. It would be a good chance to get the basics about what is involved in law school, and meet some students who might be willing to share their experience. It might even be possible to sit in on a class or two. There is a lot you can do with a law degree aside from being a trial lawyer and this could also give you the pros and cons of some of those opportunities.
You could also contact your local law clinic and inquire about volunteer opportunities or internships. That might give you a taste of what it is like. If nothing else, maybe one of the attorneys would be willing to let you shadow them for a career day or discuss their experience as a lawyer. Same with any other lawyers you might know (family, friends' parent, parents' coworker, etc.) Most trials are also open to the public. While most are as boring as watching paint dry, it would give you a glimpse into the trial process, and that it isn't all Perry Mason and Law & Order.
Talk to your guidance counselor to see what your school has to offer.
