I strongly second the last point.
I was a lot like you (I'm addressing this post at the person the whole thread is about, not Thomas) for the second half of high school. I had a lot of fun hacking on various projects, was quite sure that CS was my future, and thought my classes--though I did find parts of most of them interesting--were mostly wasting my time. I talked about wanting to quit, and if I had a successful project that started bringing money in the door, I might have.
One trick is that I did care very much about my grades. So after some wavering about whether I wanted to go to college or push it off indefinitely, I decided to go to Stanford. And for reasons that I can't entirely explain, I signed up for a program where I spent freshman year reading a sizable portion of the important Western writers of the past 2500 years. And I realized that I actually really like the humanities when done well.
But I was still pretty set on a career in tech startups, took mainly CS aside from that program, and flirted with dropping out a couple times.
Now it's my junior year, and I've slowly realized that there are a lot more options out there that interest me. I gained an appreciation for the academic side of CS. And I realized that I really do like and care about thinking and writing about social issues, philosophy, and some other things.
I've pretty much determined that my dream job is professor because it would let me do everything I like doing (innovate technically, communicate, teach people, mentor people). However, I'm also probably not going to go down that track because of the hazing (grad school + difficulty of finding academic jobs afterward) and inflexibility (in the good case, you probably only have one great job offer in one place, and you'll pretty much be there for life), but if you had asked me freshman year, I would have said I had no interest in research.
I'm also not sure that I want to stay in tech forever. There are a lot of interesting problems, one person's contributions can be meaningful in some settings, and it's very flexible and well-compensated. However, a lot of what people are doing is pretty boring to me on most levels (most companies don't need innovative technology, and even most of the ones that are innovating aren't particularly doing anything for society that I care about). After a decade or two, there's a good chance I'll want to do something more interdisciplinary and with more social value. I definitely am not convinced startups are the thing for me; the vast majority of startups just seem banal at this point, though there are some gems.
This also ties into the fact that I expect the world to change a lot in my lifetime. Tech is important to me now, but as the world changes, that could change too, and the more freedom I have to do that, the happier I'll be.
I've learned a lot about what there is in the world and what I care about in the last five years thanks to being in school. And I have a great foundation that will make it easier for me to follow my interests as they develop.
As a side note, college has been an extremely important time for me as a person. I felt pretty adult as a senior in high school, and in many ways, I was; I was far more responsible and better at avoiding stupid decisions than most of my classmates. But I still had a lot of growing up to do, especially socially. I don't think college is necessarily the optimal environment for that development, but it's a very good one. Make sure that you have friends about your age, whom you frequently see in person, and spend significant time with. Get close to some of them.
Finally, writing well is extremely important and useful no matter what you do. It is worth the investment, and the earlier you invest, the more it will pay off.