I'd recommend taking a look at the answer to this question on whether colleges recalculate GPAs. Ivy League schools don't have a special GPA recalculation process that differentiates them from other colleges. They'll just look at your GPA as recorded by your high school and then consider it in the context of the difficulty level of the courses you've taken and how challenging your school is known to be.
You're correct that if your high school is extremely competitive, an A- average may be viewed more favorably than an A average at a school that is less so, but there's no definitive system that says "an A- at School X = an A+ at School Y". Likewise, I don't think colleges are putting more emphasis on standardized testing, especially considering the fact that the SAT has changed so significantly in the past year. Test scores and GPA are still of relatively equal importance in the application process. Just remember that with GPA, the number itself isn't all that significant - it's the levels of the classes you took to get there, your rank compared to other students at your school, and, as you mention, the reputation of your high school in general.
My advice is to worry less about comparing yourself to students at other high schools (and avoid describing whole groups of people as "unmotivated"). Just continue doing the best you can in difficult classes and getting ready for standardized tests. There is no exact formula for acceptance into a top ten school, but chances are if you're this concerned about it you're probably doing just fine. If you haven't already, you can also read Allen's article on how to get into these highly competitive schools - it sheds a lot of light on the process.