Take every AP exam available, that will knock off all the easy classes in college that will equally waste your time and you can get out of some high school classes now and do it as independent study. I took 5 or 6 in my junior and aced them all - including two for subjects I had never even had class in. Just pick up some princeton review books and go at it. By the time I got to college I had 40 credits already done.
They had some fairly decent AP classes at my school that were challenging enough if you took several of them. I remembered thinking the first 11 years of school were a waste, but the last two weren't bad.
Don't even worry if your school doesn't offer the class for it. A friend of mine and I did self-study for one AP test, and started about 3-4 weeks before the text. I didn't "ace" it, but I got a high enough score that it got me out of required classes in college.
True, also the definition of "aceing" should be adjusted for the AP exams. I took the Physics C Electricity & Magnetism exam without taking the class, you only need to get something like 65% of it right to get the highest score (which some shockingly small percentage of people even do). That isn't hard at all if you put your mind to it. When I got to college it knocked off a 4 credit class with a 3 hour lab each week. 2 weeks of studying saved me hundreds of hours of work in college.