Punya S R
I know people who were in a similar situation like you, so I think that I would be able to answer this question.
The top CA Coaching Institutes in the country need a specific (and high) percentage of marks in Grade 12.
But, not all the institutes have the same requirements.
If you are really sure that you definitely want to take up CA, then I would suggest that you approach institutes who do not have high Grade 12 % cut-offs.
All the best, in your endeavours!