Can I boost my GPA from 3.3 to a 3.9 in two years?

This is a simple math problem so you can follow along easily.

By the time you apply to Cornell, you will have almost completed 7 semesters if you are applying RD. And if you are applying ED, your 7th-semester grades will not be available by Nov.1 so you will have completely 6 semesters.

So if you get perfect 4.0 report cards for the next 3 semesters, the math problem will look like (4(3.3) + 3(4.0))/7 = 25.2/7 = 3.6 UWGPA. So the theoretical max you can have is an unweighted GPA is 3.6 shy of the 3.9 you want. I won't do the math for the 6-semester version but it's 3.533 max which is even less.

Let's say you take 10th grade over, and get a 4.0 for 10th grade, then you will have (2(3.3)+5(4.0))/7 = 26.6/7 = 3.8 WGPA. It still doesn't get you to a 3.9 but it's a very good GPA that certainly all colleges will look at since you show some sacrifice and willingness to correct your errors and have a perfect upward trend. Will Cornell let you in with a 3.8? It's possible but keep in mind that your grades and coursework are only 1 of many important elements for Ivy admissions. You are going to need great ECs, Essays, Recommendations, and Test Scores.

I don't know how badly you want to attend a Top college but now is the time to have that discussion with your parents and decide if repeating a year of high school will be a productive use of your time that will make a difference in your life. I don't say this lightly. Some people might say, Hachi forget about more HS, apply and get into a competitive college and then transfer to Cornell. That is certainly a possibility. Luckily for you and other potential transfer students, Cornell's transfer rate is like 18-19% (2020) and that's a lot higher than their admit rates which dipped below 9% (8.62%) the last cycle. I still would seriously consider doing a "do-over" for 10th grade.

https://www.koppelmangroup.com/blog/2020/1/24/transferring-to-cornell-university

To make things easier, might I suggest applying to some great schools in upstate NY. You have a choice of Syracuse, Colgate, Hamilton, Skidmore, Union, Vassar, Hobart & William Smith, Bard College, and Marist. It would be a great accomplishment to get into any of those. If you do well after a 1 year, I'm sure you'd be a strong transfer candidate to Cornell.

Good luck and hope that my reply was more positive than negative.

how did it go?

The best way for you to answer this question would be to use a GPA calculator. My personal favorite is https://www.collegesimply.com/gpa-calculator/college-gpa-calculator/

When I want to know what GPA I will have by the end of senior year, I enter in my current GPA and how many classes make that up. (My school is unweighted and uses quarters so this is easy, but if your school is not this simple, I recommend using the number of credits you have earned so far, and when calculating new classes into your GPA continue to use credits, which is especially easy when you are experimenting with all A's) This calculator then allows you to add eight classes at a time. Determine how many classes (or credits) you intend to take, and add them eight at a time, changing the "prior cumulative GPA" to the new one you just calculated and adding eight to the "number or prior credits completed". Once you've added all of your classes you'll know what the highest GPA you can mathematically get is.

Obviously, this is only one (rather complicated) way to calculate this, play around with this calculator or find others to meet your needs. Good luck!

Yea, I agree with @CameronBameron. It is basically impossible for you to bring your GPA up by that much, especially considering the fact that you apply before you even finish the first semester of senior year, which gives you even less time. You can still apply to Cornell though, just make sure to do everything else (essays, personal statement) well and that you show an improvement in your grades. Also, if you have the time (so you won't negatively impact your GPA), you can strengthen your extracurriculars. Maybe go win an award (and yes, I know it's not as easy as it sounds) or become the leader of a club. Although it's not guaranteed, if you work hard and try to improve everything else, then you might have a higher chance at Cornell.

you definitely can