How to maintain a 4.0 GPA in high school?

Well I have maintained a 4.0 GPA throughout my whole 3 years as a middle schooler, well this year I will be attending high school (I'm so excited!) and I want to maintain a 4.0 GPA in my 4 years as a high schooler. I really want to do this because it will help me to apply to a good university (I want to become a neurologist)... the hard part is I'm taking all honor classes (9th graders can't take AP) with biology and Algebra II/ Trig. The other hard part is I live in a really rich area, so all the kids that I will attend high school with are really smart. Almost all of the students end up going Microsoft, Boeing or a doctor. So that means the teachers have high expectations. How can I acheive this goal?