The Ivy league colleges are quite selective on their admissions, and the competition is fierce. Usually, thousands of students apply for only a few coveted spots.
If you have a great GPA at your high school (3.7 or above), and if your high school has a top rating in your state, you should be able to maintain a good GPA at an Ivy league school.
You have proven that you can do the work, but remember you will need to do more in college. Many advisors say that you need 15-20 hours per week per course. The key factor is to make sure that you have a "balanced" course load. Some students can take 3 hard courses (e.g. math and science) in the same quarter/semester, but if lab time is required it is better to only take two. If you see yourself falling behind or not comprehending the material, it is very important that you don't wait until the last minute to ask for help.
I like that you are being proactive, and I am sure that you will do well! Let me know about your progress, and feel free to ask me any other advising questions.
Last updated Dec 13 '17 at 11:02 PM