I left school after the 11th grade for what appear to be the exact same reasons. In the twelfth grade, I was 'homeschooled', I did a lot of independent study (AP English, AP Computer Science, Science-Fair, I attended the National Youth Leadership Forum on Technology), and I took three college courses every quarter. (Physics, Chemistry and Engineering).
It was an immensely challenging year, and I had a lot of free time to learn what I wanted, and work an interesting challenging job on the side. When I applied for college, my parents wrote a letter saying what I did, and I had college transcripts to back it up. In my state, if you take college classes as a high school student they call it 'Post Secondary Enrollment Options Program' and the taxpayers pick up the tab.
I also only spent three years in college for the same reason; I started feeling like I was wasting my time. That may or may not have been true, at college I could have applied myself more and used more of the resources around me (most professors are professors because they are very good at what they do...learn from them, not necessarily from what they teach in class).
Some of it is probably you, and some of it could be the place/people you're around. This is very hard to look at objectively.
People aren't unreceptive to high school and/or college dropouts. People are unreceptive to slackers, and underacheivers. Honestly for me it just doesn't come up much, unless people ask 'Where did you go to school?' and by then they've usually made up some sort of decision about what to think of me anyway.
Dropping out of school has not closed one opportunity to me. At least not one opportunity that I would have pursued anyway (probably some big corporations have restrictions on that sort of thing).
What it comes down to is this: Do what you want. When your guidance counselors tell you "If you had all the money you would ever need, what would you do?" Don't mistake that to mean, 'after high school, after college, after this certain point in your career'. That means "right now, what are the steps that I need to take to make that happen" and doing them.