Suggestion: Provided the finances are there*, go to University as soon as you graduate. Ask your parents for advice on choosing a major - specifically, you should be willing to pick one you're unexcited about but which they think looks good. Maybe get a transcript from High School to help guide your choices here; look at something related to better grades you got. However, be very clear that you might change your mind midway through your education - emphasize that you're willing to let them guide you, but you're still going to make your own decisions if experience gives you more information. You should try to communicate that you're grateful for their efforts (even if you
aren't) but that you are also being honest about how your future choices might go.
There are a bunch of reasons for this. Most importantly, you probably aren't going to know what you want to do anyway when you get to college. And that's actually fine, but parents will freak out. You can very easily change majors midway through, and unless you were very late in the program you're unlikely to need to stay late (worst case, an extra semester). To facilitate both this and figuring out what you want to do, take your elective and general education courses as soon as possible. These are the courses that aren't directly related to your major, but which all universities require in order to make you a "well-rounded student" - you should vary these as much as possible to get exposure to a variety of different disciplines, which should help you get an idea of what options you have. Essentially, you don't have to know what you want to do with your life while you're there. In fact, you don't have to know what you want to do with your life by the time you
graduate. You just need to know what skills you want to get out of your degree, and that's a much less crazy-huge decision. Career aside, you just need to think of something it would be awesome to know how to do.
For handling parents, you need to approach everything from their perspective - they are going to see themselves as wanting to help, and deserving consideration for everything they've done for you. They may also have a sense that they deserve some control over your life. Everything you
say should be from the perspective of "What will make my parents happy", even if that's not what guides what you actually
do. That means, instead of approaching the conversation from the assumption that you're trying to do what's best for you, you should aim at explaining why it's best for your parents - that means emphasizing that you want their guidance, that you're not going to mislead them with promises you can't be sure you'll keep, and that what they want is a factor in your own reasoning. Letting them make what is essentially a meaningless choice (your initial major) is a great way of giving them a sense of importance without compromising your actual future, provided you give them enough forewarning that a change of major later on doesn't feel like a betrayal. If you can, put it in writing or e-mail or something so that you can bring it up if they
do act like it's a betrayal.
In any case, however, you're still a 2nd-year high school student. You don't even need to feel responsible for knowing any of this. Just focus on getting through the year, and then the next, and at that point maybe start paying attention to what university to go to for which major.
*If they are not, go for employment if you can find a job that will permit you to save money, or else go to a community college or something else more cost-effective than university in order to get your general education requirements out of the way. Meanwhile, to get a feel for what University courses are like and to sample different disciplines,
look around here for lecture videos and such things in your spare time. Absolutely do not go tens of thousands of dollars into debt for a university education without having a goal in mind that you think is worth it. Be adamant to your parents on this matter.