How do you like the school where you are currently studying?
My inclination would be the same as suggested by @coffeeat3. I think that you should do as well as you can at your current high school.
At least in my experience highly ranked universities in the US have students who come from a very wide range of high schools. Highly ranked graduate programs in the US have students who come from a very wide range of undergraduate universities. There are risks and costs associated with changing high school half way through. Doing well where you are is IMHO more likely to produce very good results.
Junior year of high school is likely to be more work both because you are more likely to be taking advanced classes, and also because you are likely to be putting significant effort into considering which universities to apply for and getting ready to take the SAT or other standardized tests. I would focus on this effort.
Best wishes.