How do I compensate for bad grades in class 11 and 12?

@InfiniteLibrary you say you are doing international curriculum. Are you doing IB? Are you aware of the grade boundaries for IB? An “80” may be a B for a US HS but for IB it may be a “7” which is the highest possible score. You will be compared only to other IB students - they do not take IB grades and look at them through the lense of a US grading system.